nr. 4 EN/2011

SUMMARY

Camelia BARBU, Roxana BUBATU Designing a pico-hydro power plant controller 2

Silviu BECUŢ, Adrian VLAD, Adrian DIDIŢEL, Attila KOVACS, Viorel VOIN RIOGUR, a successful product of MAXAM Romania as solution to improve efficiency contouring blast in quarrying and underground 6

Dumitru FODOR, Gavril BAICAN Open cast exploitation of lignite deposits under difficult hydrogeological conditions 12

Dacian MARIAN, Ilie ONICA, Eugen COZMA New profile function for ground subsidence assessment in the case of underground coal mining 24

Ciprian NIMARĂ Anthropic impact assessment on the tructure and morphology of the eastern region of Petroșani mining basin 34

Constantin NISTOR The management of areas affected by mining industry in the Oltenia coalfield 40

Viorel VULPE Possibilities of use of remaining gaps in the open pit 47

Vasile ZAMFIR, Horia VÎRGOLICI, Olimpiu STOICUŢA The positional synthesis of the slider-crank mechanism 54

Personalities among us “A dream come true”- Prof. Ph. D. eng. D.H.C. Ştefan Covaci at the age of 90 years old 58

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DESIGNING A PICO-HYDRO POWER PLANT CONTROLLER

Camelia BARBU*, Roxana BUBATU**

Abstract: The objective of this paper is to design a Pico-hydro power plant controller based on his mathematical model. First, the natural hydro process is considered consisting of water lake, supply pipe, hydro turbine, DC generator and controller. Second, for each part of the Pico-hydro is written the mathematical model and after that the entire system is simulated in open loop. Then the controller is designed and the system is simulated in closed loop. These two control modes are compared and presented the advantages of each of them. The simulation results are as expected and can be used to design and validate the controller. Keywords: renewable energy, mathematical model, simulation

Introduction The Pico-hydro means a plant of small power, having no more 10 kW representing lately the biggest challenges in clean energy generation, due to the following advantages: Use sources of low water flow and fall and are

environment friendly ; Can autonomously function and useful for

isolated areas; The initial investments are low.

The Pico-hydro plant has the following important elements: water lake and vane; supply pipe; hydro turbine; DC generator and controller.

Fig.1. Pico-hydro power plant: the real situation and the diagram

In this analysis we will consider the above case of a DC generator with a common power bus.

The Pico-hydro plant can be considered as a system with the block diagram from fig.2.

Fig.2. Pico-hydro system block diagram

The water lake has as input a qx uncontrollable flow and as output a vane that controls the h water level in the lake, producing a qv controllable flow. There are two water levels: the minimum N0 level and the maximum N1 level. The water level h must be controlled by the on/off position x of the vane between these two levels. The second component is the hydro turbine, ____________________________________ *Lect.eng.Ph.D University of Petroşani **Eng. Ph.D student University of Petroşani

which is a nonlinear element, having as input the hy pressure and as outputs the MT torque and the ωT speed. The DC generator is a nonlinear element, too. The inputs of the generator are the MT torque, the ωT speed, the Φ control flux and the output is the DC power P. The controller has two inputs, the h pressure and the ωT speed and two outputs, one for on/off control of the vane and the other for generator flux Φ control.

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Revista Minelor - Mining Revue no. 4 / 2011

Mathematical model for hydraulic process In this section we will model and simulate the hydraulic process of power plant and we will present the simulation results. Considering the volume V, surface S and level h of the tank, we can write the relationship:

Vx qqdtdV

−=

In order to model the on-off control principle of the vane we will introduce in the above relation the step distribution )(xθ , resulting:

)(1 xhk

q VV

V θ⋅Δ⋅=

With SkThhhSV VV ⋅==Δ⋅= ,, , we get the mathematical model of the process and the transfer function:

xVV qkθ(x)hdtdhT ⋅=⋅+⋅

⎪⎪⎩

⎪⎪⎨

⎧

=⋅+

=⋅

=

⋅+==

)(1)(;1

)(0)(;

)()()(

vaneopenedxsT

k

vaneclosedxsT

ksTx

ksqshG

V

V

V

V

V

xW

θ

θ

θ

Fig.3. Simulation of hydraulic process: a) model; b) simulation results

Mathematical model of the DC generator

We begin from the hydraulic turbine

equations, in linear form, where a and b are constants. When only the qT flow and the ωT speed are modified, we get the mathematical relations for torque:

TTT bqaM ω⋅−⋅= In dynamic regime the dependence between

torque MT and pressure hy can be written to a linear differential equation:

yTTT

T hkMdt

dMT ⋅=+⋅

where: TT is time constant and kT is the steady state gain. Results the transfer function of the turbine:

sTk

shsMsG

T

T

y

TMT ⋅+

==1)(

)()(

In fig.4 are presented the modeling and simulation results for the nonlinear and linear approach, having the following data: a=400, b=1.5, k1=300, k2=50, k3=0.02, k4=0.03. In this simulation we will consider the input hy constant of 5 m and the input ωT

fluctuating between 7 and 8 rad/s. As outputs we will represent the MT torque and the qT flow. The torque is presented both by nonlinear and linear model in order to see the approximation done by linearization. As can be seen, these differences are acceptable, so in the following paragraphs there will be used the linear approximation. Second, we will write the DC generator mathematical model. This because the Pico-hydro generally use the DC solution in order to charge the batteries. The generator equations for the input torque MT and the outputs voltage U and power P are as follows:

dtdiLiRRkU GLGTe ⋅−⋅+−⋅Φ⋅= )(ω

ikM mT ⋅Φ⋅=

dtdMM

kLM

kRRMUiP T

Tm

GT

m

LGTT 22

222 Φ⋅

−Φ⋅

+−ω==

where: Φ, i and U are generator’s flux, current and voltage; RG and LG are internal generator’s resistance and impedance and RL is the load. In this case LG can be neglected.

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Fig.4. Hydro turbine, model and simulation results

In order to maintain an approximately constant output voltage, there can be introduced a loop on speed. In fig.5 are presented the model and

simulation results for the two cases, open loop and closed loop.

Fig.5. DC generator: model and simulation results

Mathematical model of the plant For modeling and simulation of the plant we consider the hydraulic and electrical parts together with the dedicated controller. This controller is based on on/off principle and controls the input flow of the turbine and stabilizes the output voltage of the DC generator.

First, we will design the controller that has two inputs and two outputs. The inputs are the pressure h and the speed ωT. The outputs are the on/off control signal for the lake vane and the DC generator flux Φ. In fig.6 is presented the controller model and simulation results.

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Fig.6. Controller: a) block model; b) simulation results

The plant complete model was obtained connecting all the elements presented above and the controller. In fig.7 are shown the simulation model and results for this system. There were used the following data: qx = 6 m3/s; S = 12 m2; N1 = 1.5 m;

N0 = 0.4 m; ω0 = 15 rad/s; U0 = 18 V; h0 = 8 m; RL = 0.02 Ω; RG = 0.01 Ω; Tp = 5 s; kT = 7.5; TT = 5 s; h = 0.5 .. 2 m; ωT = 18 .. 20 rad/s. The system can run in two modes that are open loop and speed closed loop. In fig.7.b there can be noticed the very good results in closed loop control.

Fig.7. Complete plant: a) model; b) simulation results

Conclusions Many years the small rivers and the fresh running water were an important life resource for the little communities around them. Today, due to the technology of pico-hydro, this running water represents also an important clean energy resource too. This paper presents a systemic approach on the Pico-hydro plant, starting with the achievement of the process and continuing with the controller design. The hydraulic part and the electrical part were modeled and simulated. Then, there is designed, modeled and simulated the controller and are obtained the simulation results for the plant. The results of this paper prove the correctness of this solution and can be used in practical applications, like controllers design for Pico-hydro plants.

References

1. Fraile-Ardanuy, J., Wilhelmi, J.R., Fraile-Mora, J., Pérez, J.I., Sarasúa, I. A Dynamic Model of Adjustable Speed Hydro Plants, 9 Congreso Hispano Luso de Ingeniería Eléctrica, Marbella, Spain, 2005 2. Pop, E., Leba, M., Tabacaru-Barbu, I.C., Pop M. Modeling, Simulation and Control of Pico-Hydro Power Plant, Control Systems, Proceedings of the 4th WSEAS/IASME International Conference on Dynamical Systems and Control, Corfu, GREECE, October 26-28, 2008, ISBN 978 960 474 014 7, ISSN 1790 2769, pp. 103-108 3. Leba, M., Pop, E. New distribution Properties and Applications in Digital Control, Proceedings of the 7th WSEAS International Conference on Advanced Topics on Signal Processing, Robotics and Automation (ISPRA’08), Cambridge, U.K., ISBN 978 960 6766 44 2, ISSN 1790 5117, pp. 43-48, 2008 4. Tabacaru-Barbu, I. C. Contributions Regarding the Modeling, Simulation and Implementation of Methods and Techniques of a Sustainable Integrated Renewable Energetic System Achievement, Ph.D. Thesis, Univ. of Petrosani, 2009

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RIOGUR, A SUCCESSFUL PRODUCT OF MAXAM OF ROMANIA AS SOLUTION TO IMPROVE EFFICIENCY CONTOURING BLAST IN

QUARRYING AND UNDERGROUND

Silviu BECUŢ*, Adrian VLAD**, Adrian DIDIŢEL***, Attila KOVACS****, Viorel VOIN*****

INTRODUCTION

The improvement of surface mining exploitation and / or in underground in Romania requires the application of modern technologies and techniques for getting the best blasting performance, both in conditions of technological efficiency and safety of staff as part of these operations.

When performing the blasting some of the energy released by detonation of explosives is consumed effectively for crushing and detachment from rock massive.

Important part of the energy is lost, for throwing pieces of broken rock into the atmosphere, in the form of kinetic energy (air shock wave), thermal and sound or, in rock massive, transforming on far the spreading from the epicentre of the explosion, in elastic waves (seismic waves).

Therefore, in designing and coordinating the blasting work should consider the following aspects: • detachment from the massive a needed amount of rock, a corresponding grain to technological requirements; • slope integrity if those as shaping careers, correct

contouring of gallery or exploitation rooms for underground mining. • protection of civil and industrial targets in the area, the effects of blasting works - air shock wave, seismic effect etc. respectively reducing the discomfort for the human factor.

On surface mining, finding the most favourable methodology has always aimed slope integrity because they will be returned to nature after reconstruction operations, at the end of blasting.

In underground mining technologies to prevent the emergence of blasting over-profiling for tunnels or galleries that achieving a good outline of the room as that does not affect the structure of the pillars for salt mines

Involving the experts from MAXAM Romania, mainly aimed at obtain a new explosive product to meet the technical criteria, also economic and security criteria when using this product, in surface work and underground blasting. This product is called Riogur FCD and used either to achieve final contours for tunnels and other underground works (galleries, chambers of salt-mining etc.), or to have correct profiling slopes for surface mining.

Figure 1. Riogur FCD. Section

____________________________________ *Eng. Ph.D MAXAM Romania ** Factory manager MAXAM România *** SHE&Q&S Manager MAXAM România **** Eng. Ph.D INSEMEX Petroşani ***** Prof.eng. Ph.D University of Petroşani

RIOGUR FCD. GENERAL PRESENTATION, TECHNICAL PARAMETERS, USE General presentation Riogur FCD is a water gel type explosive having as main oxidant ammonium nitrate and as the main fuel nitrate mono-methylamine and is the

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latest development in technology of micro-gels. In the cartridged explosive mass is enclosed a detonating cord with an explosive load of 6 g/m, designed to ensure explosive continuity, flexibility, and improved transmission of ballistic performances (figure 1). Technical parameters The main technical characteristics of this explosive are: - Detonation velocity 3300 - 3800 m / s - Density 1.15 to 1.18 g/cm3 - Transmission of detonation: 6-9 cm - Work capacity (mortar ballistic): 65 - 72% - Gas volume: 932 l/kg - Toxic gas content: 2,27 - 4, 67 l/100g

The explosive Riogur FCD was tested and certified in specialized laboratories INSEMEX Petroşani. Riogur currently are manufactured in these sizes and cartridge lengths: Ф17mm x 500mm, Ф22mm x 500mm, Ф26mm x 500mm, Ф32mm x 500mm, Ф45mm x 500mm. In special situations, can be manufactured and sizes Ф29mm, Ф38mm and Ф40mm. Packing

Products are packed in special cardboard boxes, 25kg or 60kg. The boxes are send to customers as pallets (figure 2). The explosive transport class is 1.1D, which is produced at Victoria, Brasov county, at Maxam Romania working point.

Figure 2. Riogur FCD. Packing

Use and advantages This type of explosive is used successfully in the blasting of pre-splitting and contouring both opening and sloping at surface works in quarries and underground works and tunnels.

Main advantages: Comparing the product, in terms of price, with other known on explosives market, certainly is the most competitive. You can use easily and has a high level of security as well as during transport. Practically the risk of non-initiation is reduced to zero due to detonating cord in its composition. Having a detonation velocity of over 3500m/ s, a remarkable thermal stability and very good resistance to water the explosive Riogur FCD is worthy take in consideration by any potential user. APPLICATIONS OF THE ROMANIAN EXPLOSIVE RIOGUR FCD Blasting theory of accounts

A blasting hole loaded with explosives creates during the explosives detonation near the load, an

area where dynamic resistance to compression is largely over-passed and the rock is crushed and pulverized. Outside this zone of transition, traction strengths generate a compression wave associated with disposal of radial cracks around the entire hole.

In the case of two holes loaded with explosives that detonate simultaneously, the radial cracks tend to propagate equally in all directions until through the collision of two shock waves in the midpoint of the two holes are produced traction complementary and perpendicular on the axial plane (figure 3). Traction in the aforementioned plan exceed the dynamic tensile strength of the rock, creating a new crack and encouraging in the direction of the designed section, propagation of radial cracks.

Subsequently, crack extension occurs by the action of explosion gases which invades and penetrates them. Preferential propagation in the axial plane with the effect of opening the gas pressure provides a cutting plane in accordance with design.

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Figure 3. Stage of tensions generated by the superposition of shock waves produced by the simultaneous detonation of two charges

Gas pressure is a key element in the execution

of a contouring blasting so it should be maintained until the complete union of cracks starting from adjacent holes, adapting the explosive load length to avoid leakage of gas into the atmosphere.

It can be concluded, that the mechanism of contour blastings comprises two distinct phenomena, one derived from shock wave action and other proceedings gas explosion between the two is maintained a causal link.

Using the explosives RIOGUR FCD in Queries

The first tests of explosive Riogur FCD on surface mining were made in the company LAFARGE AB, with the site Suseni Query. The exploitation was carried out in an andesite rock, stratification structure of rock and its degree of fracturing is highly variable from one area to another. The average density is 2.5 to 2.6 t/m3 which gives the rock a plastic behaviour, which depreciating the explosive cutting ability.

The presence of clay layers with variable thicknesses influenced a seriously the resulting rock granulation after blasting.

During the operating phases the detonation system was changed by mainly modifying the drilling network and the way of initiation of the blasting network.

In the blasting works the explosive Riogur FCD was used in two types of applications: • blasting work for achieving final slope of the query • blasting work to achieve designed production

In the first blasting applications work aimed to obtain final slope of his career, slope located approximately 8 to 10 m from the county road that connects towns Suseni and Odorheiul Secuiesc.

The main parameters of the blasting are the following. • Height of steps: 14 m • Anticipate: 2,5 - 3,5 m • Number of holes: 27 • Number of lines: 1 • Hole diameter: 76 mm • Distance between holes: 2.2 m • Contouring explosive: Riogur FCD diameter 45 mm • Initiation: detonating cord of 6 g / ml

The charge design inside the hole is shown in figure 4.

After the blasting has obtained a linear slope, with 60 m length without affecting the integrity of the road or nearby soil.

Later in that area was built a parking lot for tourists, a place called "Belvedere".

The second application targeted the use of Riogur FCD explosive in current production work.

It was noted that the basic conditions of use explosives because of their current work blasting the rock crackling behaviour increased after blasting results over- crackling approximately 3-4 m behind the front.

This leads in addition to the emergence of oversized rocks results after the first blasting and the difficulty of drilling holes for the next front line work.

Therefore it was decided to use explosive FCD Riogur diameter of 45 mm on the last row. For it has changed the drilling scheme and how to load and start the boreholes.

Production holes were drilled with 92 mm diameter and the contour 76 mm diameter. Also distances between holes on the same line were different; the distance between production holes was 2.8 -3 m and in the contour of 2.2 m.

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Figure 4. Contour charge design inside the hole

In production holes the explosive column was built with Elexit, Riogur and Nagolită and in contour holes was introduced Riogur FCD at 45 mm diameter and one cartridge Riogel 60 mm diameter on the basis (see figure 4).

Initiation of explosive charges in holes was achieved with non eclectic systems type Detinel.

Scheme shown in Figure 3.3 is applied in career blasting.

After application of this technology behind it was noticed the disappearance of front crack, making a regular slope along the length of the front and resulted the reduction of oversized rocks after blasting.

Figure 5. Blasting monography

Empty Volume

Fitil detonant sausistem neelectric

Buraj

Start

60x500 mm1 cartus de Riogel

Riogur 45x500 mm

Legatura intre Riogel si Riogur

Obturator de plastic sau h rtieâ

Conexiune cu fitil detonant de 6 g/mlsau cu conector cu aceiasi int rziereâ

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Underground use of RIOGUR FCD explosives

RIOGUR FCD explosive underground testing was performed at Salina Ocna Dej, belonging SNS Bucharest, given the high production of salt is operated over a year and that is the complex salt in Romania.

Salt blasting technology in Ocna Dej is developed in quadratic form rooms, with a length of 15 m and a height of 8 m.

The main purpose of these tests was to see the behaviour and efficiency of explosive Riogur FCD 22 mm in the exploiting room contour area.

It was proposed a blasting scheme with parallel holes, using as base load Amonita E and for contour holes was used Riogur FCD 22 mm.

The main parameters of the blasting are: - Total number of holes: 112 - Length of hole: 2,0 - 2,1 m - Hole diameter 40 mm - Base explosive: Amonita E (32x220mm, 200g/cartridge)

A quantity of explosive / hole: 1,0 - 1,2 kg - Explosive contour: Riogur F-CD 22 - Ignition: Electric Detonators type Riodet S - millisecond

The load method of the mine hole is shown in figure 6 and the blasting schemle is shown in fig. 7

Figure 6

0 0 0 0 0 0 0 0 0 0 0 0 11

2 2 2 1 1 1 1 1 1 2 2 2

4 4 4 3 3 3 3 3 3 4 4 4

6 6 6 5 5 5 5 5 5 6 6 6

8 8 8 7 7 7 7 7 7 8 8 8

9 9 9 9 8 8 8 8 9 9 9 9

10 10 10 10 10 9 9 10 10 10 10 10

11

11

11

11

11

11

11

11

11

11

11

11

11

1112 12 12 12 12 12 12 12 12 12 12 12 12

1,26 1,26 1,26 1,26 1,26 1,26 1,26 1,26 1,26 1,26 1,26 0,80,8

0,35

0,65

1,00

1 ,0 0

1,00

0,20

0,15

A - AA

AB - B

B B

Figure 7. Blasting scheme with parallel mine holes

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Conclusions

The use of Riogur F-CD explosive for contour holes results in a much better profile uniformity and a whole wall jump blast. Thus avoids the appearance of over or under profiling and as default correct sizing of pillar.

There were no black traces on salt to affect the organoleptic quality of salt in the holes contour area. General conclusions

To minimize damage of the surface work slopes, damage to the gallery or tunnel wall or salt mining pillars where there are different ways of detonation that reduce their destabilization. It is obvious that these methodologies, normally lead to a higher cost of operation, although some can be recovered by the time gained would have been dedicated to cleaning the place after blasting.

An additional cost is not to be neglected in appearance of the over-profiling situation in underground works where necessary additional

work to roof support or re-profiling, in which case further increase costs considerably.

Using Riogur FCD explosive in both blasting technology at the surface and underground showed that this product is a viable cost reduction solution.

It should be noted also that the use of this product helps to limit the effects of mining structures and also limits the effect on civilian objects or industrial blasting in the immediate neighbourhood of the mines. References 1. Nasca, F. Teoria de la voladura de contorno, Madrid, Spania, 2010 2. Becuţ, S., Kovaks, A., Hegedus, N., Ranete, A. Improvements on blasting technology in Ocna Dej salt mine (Romania) applying modern MAXAM explosives, „Drilling and Blasting technology 2010” 10th International Conference, Hungarian Society for Blasting Technology MARE, Balatonkenese, Ungaria, 2010 3. *** Technical Product Specification of RIOGUR FCD, Maxam Civil Explosives, Spania, 2009

11


OPEN CAST EXPLOITATION OF LIGNITE DEPOSITS UNDER DIFFICULT HYDROGEOLOGICAL CONDITIONS

Dumitru FODOR*, Gavril BĂICAN**

Introduction

The lignite deposits of Oltenia are the most important coal deposits of Romania. These deposits are included in the structural unit of the Sub-

Carpathian depression within the area between Danube River and Olt River occupying a total surface area of about 4,500 sq. km in three counties: Mehedinti, Gorj and Valcea, fig.1.

Fig.1 Mining Basins of Oltenia with corresponding mines and open casts

As for the geology, Oltenia deposits belong to the Pliocene formations ( Dacian, Romanian and Pontian) and consist of 21 layers of coal with variable thickness and extension, separated by soft, cohesive and non-cohesive waste rocks, predominantly clayous and sandy ones.

The thickness of the lignite layers is varying between several decimeters to several meters occurring either as a compact mass or as several coal beds constituting the layer complex, figure 2.

Fig. 2 Geological cross section through Rovinari Mining Basin

The lignite layers are numbered from bottom to up following the sequence of the deposition; A,B,C,D and I…. XVII.

The A,B,C and D lignite layers belong to the Pontian , the I,II,III and IV layers are found in Dacian, the V-VI and VII-VIII layers in the Lower Romanian while the IX-XV layers in the Upper Romanian.

Of the 21 lignite layers the V-VIII layers are exploited in te meadow zone while the V-XII layers are exploited in the hilly zones. The volume of the lignite reserves of Oltenia known by geological and hydro-geological ____________________________________ *Prof.eng.Ph.D University of Petroşani **Ph.D eng. University of Petroşani

exploration works is 2,852 millions tones with parameters allowing their categorization as balance reserve.

Oltenia lignite is characterized by the following qualitative features: - average heat power : 1,700 – 2,200 cal/kg - waterless ash content: 34-38%; - humidity; 39-45% - sulfur content: 0.8-1.2% - volatile matters : 17-23%^

The lignite deposits of Oltenia are classified based on the geological, geographic and economic criteria in five mining basins as shown in fig.1 Several perimeters have been outlined within each basin, depending on the zonal characteristics of the deposits and exploitation possibilities.

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Of the total promulgated lignite reserves , more than 80% are mineable in open casts while the remaining 20% are mineable by underground methods. During the last years, 90% of the lignite production of Romania was obtained in 16 large open casts located in Oltenia zone, between Olt and Danube Rivers.

The mines and open casts of Oltenia are reporting to SNLO – Tg Jiu and to the three large scale energetic complexes of Rovinari, Turceni and Craiova.

For the lignite deposits of Oltenia consisting of mineable shallow layers of 1.0m up to 8.0 m thick and located in a favorable environment, the open cast method was selected.

All the open casts have been designed with production capacities ranging between 0.5 million tons per year ( Berbesti open cast) and 4,4 millions tons per year ( Rosia de Jiu open cast).

Depending on the relief conditions and the vertical distance from the surface to the last mineable layers , the open cast depth is ranging between 40 and 110m in the meadow zones and up to 180 m in the hilly zones with a stripping ration for the whole mining field ranging between 3.5 in case of Tismana and Lupoaia open casts and 8.1 c.m waste / ton of of mined out lignite at Berbesti open cast.

Fig.3 Overview of an open cast equipped with continuous technological flow-sheet

Today, all the open casts of Oltenia are equipped with continuous flow-sheet technologies, figure 3 characterized by the following elements:

• Excavation of the mining bulk is performed with rotor excavators of different sizes and technical characteristics which provide efficiencies between 1200 and 4500 m3/h: SRs 470

5,315 ; SRs 1300

5,326 ; SchRs 1400

730 and SRs 2000

730 .

Predominantly, there are used excavators with 1,400 l bucket – more than 50% excavations are carried out using this type of excavator.

The excavation operations are characterized by: - exploitation of benches of up to 25m high where the haulage level is cut; - exploitation with sub-benches of up to 10 m high - exploitation with benches of up to 7 m high when cut beneath the haulage level

The excavation block width may reach 60 m while the working face length could be 2.0 km.

• Transport of the mining bulk excavated on the working faces to the storage sites is performed using belt conveyors with the belt width between 1,200 mm and 2,250 mm ,conveyor speed

4.19-6.15 m/sec and transport capacities of 2,500 c.m/h up to 12,500 c.m/h using separate circuits for waste transport to the dumps and useful material to the storage site

The belt conveyors are located on the exploitation benches and there are several options: - one single belt conveyor along the whole mining face - two belt conveyors, one along the excavation face - two belt conveyors end – to – end mounted

The open casts are also provided with different installations required for the transport operations: movable loading installations, track carriages, belt riders, etc.

• Waste storage on waste dumps using dumper machines with capacities between 2,500 and 12,500 c.m/h and useful storage in coal stockpiles using the stockers , the take over installations and combined ones which capacities range between 1,250 and 5,600 c.m/h.

The dumpers are provided with booms of 60,70,95,120 and 170 m long. The 120m and 170 m boom dumpers are used for stockpiling the waste by reloading it in the internal dumps.

The modern technological flow sheet of the operating open casts are more simple or more complicated depending on the land morphology,

13


thickness of the overburden, number and thickness of the mineable lignite layers of the area, excavation capacity and sizes of the equipment.

In some open casts where the lignite layers are well individualized the technological flow-sheet could be organized in a simpler manner, that is each excavator is working only in the waste or in coal, on benches constituting separate technological lines.

In other open casts the coal layers are separated by waste intercalations in several benches resulting in difficulties of exploitation with negative consequences on the coal quality and productivity of the excavation equipment.

In many open casts, both excavation of the waste and coal separate benches and the selective- alternative excavation – namely coal and waste on the same bench and using the same excavator- are carried out.

Usually, there are selectively mined the little thick layers (1.0m) and the waste intercalations with thickness over 0.4m.

The following exploitation methods are used in the open casts of Oltenia mining basin. • The exploitation method with the transport of the waste to external dumps – it is used in the lignite open casts where the final level of the open

cast floor has not been reached yet and thus, there have not been provided the premises of the internal dump formation. Currently, this method is used at Pinoasa and Berbesti open casts. • The exploitation method involving the transport of the waste to the internal dumps – method used in Garla, Rovinari Est, Panga and Ruget open casts, fig 3. • The exploitation method with transporting part of the waste to internal dumps and the other part to the external dumps – currently used at Jilt Nord, Rosiuta , Oltet open casts. • Combined method with partial reloading of the waste to the internal dump and partly transporting the waste to external dump – currently used at Tismana II open cast • The exploitation method transporting part of the waste to the internal dumps and partial reloading of the waste at internal dumps , fig.4 – currently used at: Rosia de Jiu, Tismana I , Pesteana Sud, Pesteana Nord and Lupoaia open casts • The combined exploitation method transporting part of the waste to the internal and external dumps and partly reloading the waste in the internal dump fig.5 – currently used at Jilt Sud and Husnicioara open casts

Fig. 4 Exploitation method using the partial transport of the waste to the internal dump and partial reloading of waste

to internal dumps Pesteana Nord Open Cast- Rovinari Mining Basin

Fig. 5 The combined exploitation method transporting part of the waste to the internal and external dumps and partly reloading the waste in the internal dump

14


The predominant methods used are those involving besides the waste transport the waste reloading to internal open casts as well.

The working benches of the open casts are 15-25m high , slope angles of 60-650 and 1,000 – 2,000 m long. The overall slope angles of the open casts range between 12 and 200 depending on the type of rocks from the exploitation perimeter depending on the existing relief conditions. In the meadow areas, the dumps were located near the final contour of the open cast and they have been built vertically with several benches, the maximum height for the deposition on the bench is 15-20m.

Depending on the characteristics of the dumped material (humidity, consistency, loosening coefficient, particle size etc) as well as on the

expected heights of the external dumps , they have been built with an overall slope angle between 6 and 90

In the hilly zones, the external waste dumps have been formed by filling the valleys near the open cast , the haulage distance to the waste dump is up to 10 km and even longer.

Today, in Romania the lignite exploitation at surface is developed within 16 large size open casts provided with continuous flow-sheet and which, depending on the market, can ensure a total production of almost 30 millions tons of lignite per year.

The production capacity and endowment of the open casts in operation in Oltenia zone is presented in the table no.1.

Table 1

Production capacity and technical endowment of Oltenia open casts

EXCAVATORS DUMPING MACHINES STOCKPILE MACHINES CONVEYORS

OPEN CAST

PRO

DU

CTI

ON

C

APA

CIT

Y

[mil.

t/yea

r]

SRs 4

70

SRs 1

300

Erc

1400

SRs 2

000

Tota

l

MH

440

0.60

MH

440

0.95

M

H

4400

.170

M

H 6

500.

60

MH

650

0.90

MH

630

0.95

M

H

1250

0.95

To

tal

Com

bine

d

To st

ockp

ile

To c

lear

Tota

l

No.

of

belts

Bel

t km

Mehedinţi 2,2 5 5 1 2 3 4 2 6 28 12,8 Lupoaia 2,3 5 1 6 1 2 3 1 1 2 28 16,4 Roşiuţa 2,5 6 6 4 4 1 1 2 42 19,4 E.M.C.Motru 0 5 7 0 12 0 0 1 0 4 2 0 7 2 2 0 4 70 35,8 Jilţ Sud 3,5 8 8 1 3 4 1 1 1 3 48 35,4 Jilţ Nord 2,5 2 6 8 1 2 3 1 1 2 42 26,8 EMC Jilţ 2 0 14 0 16 0 0 1 1 5 0 7 2 2 1 5 90 62,2 Gârla 0,8 2 2 1 1 2 9 6,1 Rovinari Est 1,7 3 1 4 1 1 1 3 23 15,2 Tismana I 2,5 1 3 4 1 1 1 3 18 12,6 Tismana II 1,5 1 2 3 1 1 1 3

4 2 1 7

12 8,4 Pinoasa 3,5 5 5 3 3 1 1 2 36 20,2 EMC Rovinari 0 2 15 1 18 3 1 1 1 7 1 14 5 3 1 9 98 62,5

Roşia 4,4 1 5 3 9 1 1 1 2 5 1 1 1 3 42 24,2 Peşteana Sud 0,7 - 2 2 1 1 2 10 6 Peşteana Nord 1,4 - 5 5 1 2 3 1 2 1 4 15 9,4 EMC Roşia 0 1 12 3 16 0 0 3 0 4 1 2 10 2 3 2 7 67 39,6 Olteţ 1,3 2 2 4 2 2 2 1 3 30 14,3 Berbeşti Vest 0,5 3 3 1 1 17 5,6 Panga 0,7 3 3 2 2 1 1 2 18 6,7 Ruget 0,9 1 2 3 1 1 2 1 1 1 3 13 4,6 EMC Berbeşti 6 0 7 0 13 1 0 0 0 6 0 0 7 2 4 2 8 78 31,2

SNLO SA Tg.Jiu 8 8 60 4 80 4 1 7 2 28 4 2 48 13 18 8 39 431 244,1

15


The Gettic depression hosting the lignite deposits form the large size water basin where aquiferous systems which characteristics depend on their position on the stratigraphical column, lithology and thickness of layers and sand benches, their water supply and the flow-rates, are encountered.

The water basin has an extended supply area situated at its West and North ends , but also inside it, along Motru, Jilt, Jiu, Gilort, Amaradia valleys , and the absence of some discharge zones determined the formation of large water accumulations as largely extended aquiferous horizons and complexes.

Because of the deposit geological structure, the complexity of hydro-geological conditions increase from West to East and from North to South.

From hydrogeological point of view the stratigraphic of the coal deposits of Oltenia indicate the presence of two well individualized horizons- the aquiferous phreatic layer and the aquiferous horizon of the IV layer floor – and of a n well individualized aquiferous complex consisting of seven aquiferous layers.

• Phreatic aquiferous horizon is well developed mainly in the water course meadow of the zone and it is spread over the extension of the alluvial deposits formed of sands and gravels covered sometimes by a clay bed which form a screen and the water courses have low catching features. It is 5-20m thick and the filtering coefficients are ranging between 1,8 – 12.5 m/day. The hydrostatic level of this horizon is at 45-60m depth depending on the water supply possibilities.

The hydro-geological investigations carried out on the deep aquiferous horizons revealed aquiferous horizons within the Dacian and Romanian formations.

• Aquiferous horizon of the IV layer floor develops in the fine or coarse sands between the layers I and IV as the coal layers II and III comprise extended areas where there is no sedimentation while the clay beds are thin; the horizon between the layers III and IV, from hydraulically point of view, are connected with the floor horizons. It is regionally extended and indicates pressures between 15 and 165 m H2O column with inexhaustible water reserves.

The hydrostatic level is between -148 and -186 and raised at the Western part of the region. Initially, in Jiului and Motrului River meadows it showed a artesian feature, but, because of the dewatering works , this feature can be found only in the low meadow zones.

The filtering coefficient is around 1.0 – 7.5 m/day, but with large variations depending on the lithology of the sands.

Aquiferous horizon of IV-V layer interval consists of one or two lens with variable extension formed of fine, rarely medium or coarse sands. The highest piezometer levels were revealed to the North –West side of Rosiuta perimeter while the lowest ones are in Pesteana zone. Because of the extended areas where no sedimentation occurred and with small thickness of layer IV and of the thin and unevenly developed clay beds of the IV layer floor, there are large surface areas where this aquiferous is hydraulically connected to the artesian horizon.

Aquiferous horizon of V layer complex is hosted between the coal banks of the V layer and its thickness may reach up to 15m consisting of fine, clayous or dusty sands.

Compared to the low V and upper V layers the aquifeorus horizon is generally separated by impervious screens , but there exist zones of direct contact with it. The flow-rates are low ranging between 0.1-2liters/ second while filtering coefficients between 0.2 and 0.3 m/day.

Aquiferous horizon of the V-VI layer interval develops over the whole region, but its thickness is low and it spreads as lens to the Northern part.

In the whole Southern zone, it develops as a layer of 20-30m thick , generally extended and constituting one of the main aquiferous horizons of the zone due to its extension and thickness.

In general, this horizon consist of 1-2 banks which are united to the South and occupy the whole interval between layers V and VI. As for the lithology, it consists of fine sands, sometimes containing also gravels, dusty sands. The hydrostatic levels range between + 136.10 m and 248.37 m.

Aquiferous horizon of layer VII-VIII interval consisting of several aquiferous sand banks with an uneven development. As for the lithology, the dusty sands and subordinately, the fine and medium size sands are prevailing. The precipitation water is fed to this aquiferous through the layer ends or the phreatic horizon.

Aquiferous horizon of VIII-X layer interval consist of 1-4 sand banks unevenly distributed. As for the lithology, the aquiferous VIII – X complex consist of fine, clayous dusty sands . In most cases, the aquiferous horizon is separated from the coal layers by clay protection screens, but in all perimeters, there are encountered zones where the sands are at a distance below 1.0 m from the coal layers or even get into direct contact with it.

Aquiferous horizon of X layer roof is hosted in the sand package and is mostly situated above the erosion base in the region on the valley sides. The thickness of the sands range between several

16


centimeters and up to 20m and is in direct correlation with the erosion rate of the region ; the bigger thicknesses are due to the sand layers of the hill crest. From lithology point of view, these layers consist of dusty and clayous sands.

Because of its position above the local erosion base this horizon is characterized by simpler hydrological conditions than the lower horizons. The filtering coefficient is ranging between 0.08 and 0.60 m/day.

The main hydro-geological parameters of the depth aquiferous layers investigated by hydro-geological show significant variations reflecting both the grain size variations of the sand horizons where hosted, and the different potential of supplying the respective aquifeorus layers and the position of the supply zones.

To illustrate it the table 2 presents the hydro-geological parameters for the main open casts and aquiferous horizons from Oltenia coal basins.

Table 2

The hydro-geological parameters for the main open casts and aquiferous horizons from Oltenia coal basins

HYDRO-GEOLOGICAL PARAMETERS Open casts Aquiferous

horizons Underground

water characteristic

Filtering coeff.

[m/day]

Breakage coeff. [%]

Piezometer pressure

[mcolH2O]

Water inflow coeff [m3/t]

Specific flow rate [m3/day]

Screen thickness

[m]

Tectonics removal rate[accid./ha]

0 1 2 3 4 5 6 7 8 Phreatic horizon free level 10-15 0,2-0,3 - 2 30-150 - none

Complex VI upward 0,1-1,0 0,05-0,1 10-30 1 10-80 0-4,0 none

Complex V-VI upward 0,3-2,3 0,1-0,15 70-100 1 8-60 10-5,0 none

Roşia de Jiu

V floor and

artesian artesian 1,0-3,0 0,1-0,18 70-200 2 20-100 5,0-20,0 none

Phreatic horizon free level 1-5 0,2-0,3 - 0 1-5 - low

Complex VI-X free level 0,1-1,0 0,005-0,1 - 1 1-15 5,0-7,0 low

Interval V-VI upward 0,3-2,0 0 10-30 1 5-15 2,0-8,0 low Pinoasa

V floor and

artesian artesian 1,0-3,0 0 40-100 2 5-20 5,0-20,0 low

Phreatic free level 3-8 0,2-0,3 - 0 5-15 - moderate Complex V-VIII free level 0,3-1,0 0,005-0,1 - 1 5-10 1,0-4,0 moderate Rovinari

Est V Floor and

artesian artesian 1,0-3,0 0 50-150 2 10-50 10-20 moderate

Phreatic free level 15-20 0,2-3,0 - 1 30-200 - low V-VI

complex upward 0,3-1,0 0,05-0,1 50-80 1 5-50 0-10 low Peşteana Nord

artesian artesian 1,0-3,0 0 70-150 2 10-70 5-15 low Phreatic free level 3-8 0,2-0,25 - 0 5-15 - low VI-XII

complex catching lens

shaped 0,1-0,8 0,05-0,1 5-15 1 3-5 0-5 low Jilţ Sud VI floor under

pressure 0,2-1,0 0,05-0,1 20-40 1 5-10 0-15 low

Phreatic free level 4-6 0,2-0,25 - - - - none V-XII

complex lens shaped free level 0,1-0,5 0,05-0,1 - 0 3-5 0-5 none Lupoaia

V layer floor

upward lens shaped 0,2-1,0 0,05-0,1 0-5 1 2-5 0-10 none

17


Further to the investigations performed in every mining basin, there resulted that most of Oltenia deposits are classified from hydro-geological point of view in the group of difficult condition deposits because of the following characteristics: • Lignite layers are hosted in soft cohesive rocks – clays and marns and non-cohesive rocks – fine, medium and coarse size sands. • Some lignite layers are overlain by several aquiferous layers and horizons • From the point of view of the filtering coefficient values there are big differences between the aquifeorus layers : small values kf <1.0m/day; medium values: kf <1.0- 3,0 m/day; and high values kf <3.0m/day • The thickness of the aquiferous layers range from small thickness (<5m) up to bigger thickness (>15m) • Pressure of the underground waters is also varying with average values (P=10-30m col H2O) up to high and very high values (P>30 m col H2O) • In case of some aquiferous horizons the static water reserves (aquiferous horizons near the lignite mineable layers) are prevailing and in some other cases, the dynamic water resources (phreatic horizon and artesian horizon of the V coal layer roof) are prevailing.

The exploitation of the lignite layers of Oltenia mining basins was and still is depending on the completion of the dewatering works aiming at: - increase of the stability of slopes and open cast opening trenches, working benches and open cast and waste dump edges - prevention of the events related to the underground water discharge in the bench slopes

resulting in suffusion of sandy rocks followed by lack of stability events; - preventing the penetration of artesian water on the open cast bottom of V layer floor

Because of the difficult and very difficult hydro-geological conditions the dewatering of the open cast fields of Oltenia is carried out in two stages and namely:

Preliminary dewatering preceding the mining works by about 1-2 years and required for ensuring the safety of the mining works throughout their completion.

In this stage there are performed the followings:

complete dewatering of the alluvial deposits where the opening trenches are excavated

diminution of the pressure of artesian waters from the sandy intercalations of the coal complex as much as possible up to the total dewatering and

diminution of artesian water pressure from V layer floor up to values which prevent the penetration of the protection screen.

Parallel dewatering is carried out simultaneously with the lignite deposit exploitation to reduce further on the pressure of the artesian waters from layer V floor and of complete dewatering of the alluvial material and aquiferous sands of the coal complexes in advance.

As dewatering works there are used surface works, respectively the trenching for dewatering for the phreatic horizon, fig.6, the large diameter and deep drill holes provided with submersible pumps, fig.7 for the dewatering of the aquiferous formations of the productive complexes and filter free drill holes with free eruption at the open cast floor level, fig.8

Fig.6 Dewatering with trenches performed in the working face 1-dewatering trenching; 2- working bench; 3- impervious rock

The dewatering trenches used at depth of 8-12 m ensuring flow-rates discharged from the massif at flow rates of about 50-250 c.m /h.

The dewatering drill holes were spaced on a 200 x 100m pattern and their depth was depending on the average thickness of the aquiferous horizon opened by the drainage drill holes and which ranged between 35-50m. The total flow-rate of water discharged from an exploitation perimeter depended on the number of operating drill holes and characteristics of the aquiferous horizon under

dewatering process and reaching values of up to 450-500 c.m/h.

The filter free drill holes with free eruption at the floor level were placed in the lowest zones of the open casts where the draining aquiferous contained under pressure water and its roof consisted of resistant rocks which enabled the completion and stability, in time, of the cavity formed throughout the drilling. The flow-rate of such a drill hole ranged between 60-180 c.m/h.

18


Fig.7 Dewatering with large diameter holes provided with submersible pumps

Fig.8 Tension release of the under pressure aquiferous horizon using the filter free drill holes

There have been evacuated so far, 14.0 cubic meters of water by ton of mined out coal, from the mining perimeters showing the most difficult hydro-geological conditions.

The presence of an upward artesian aquiferous horizon in the V layer floor, representing actually, an inexhaustible water reserve requires a technical solution ensuring the safe exploitation of this lignite layer which, only in Rovinari Basin, host a balance reserve of more than 300 millions tons.

In practice, it is about the tension removal of the aquiferous layer from the V coal layer floor and the determination of the open cast floor opening up to a limit that avoid the breakage of the protection screen. An eventual breakage of the protection screen would have resulted in the water penetration in a random manner, in the open cast and its total and final damaging.

Sizing of the open cast opening at the floor

In the open cast with artesian water in the

deposit floor it was necessary to make calculation

and measurements to establish a correlation between the artesian water pressure , protection screen thickness of the open cast floor and the opening of the open cast floor for the development of the technological flow-sheet under safety conditions.

As the screen thickness could not be influenced, there was necessary to act on the other parameters and namely: tension removal of the artesian aquiferous horizon reaching admissible values and reducing the opening of the open cast floor, fig.9.

To remove the tension of the under pressure aquifeorus layer there was performed the working technology with drill holes free of filter with free eruption at the level of the open cast floor which proved to be efficient both from hydrodynamic and technical – material point of view; their construction is simple and reduced technical features and consequently require lower costs than the classic filter drill holes.

Fig 9 Sizing of the open cast floor opening

19


The presence of aquiferous rocks with pressure water in the deposit floor determines that the resistance of such a floor reduces under the normal values for the same rocks under unsaturated condition, and in case that the impervious protection screen is too thin, the water pressure can cause the belly out and even the breakage of the floor with worst impacts on the production continuation.

To avoid the breakage of either the floor or the protection screen the following relation must be completed:

Уa. P< уe . he where: Уa- specific density of the water, tf/ c.m

P – hydrostatic pressure of water from the aquiferous under pressure layer situated beneath the open cast floor , m col. H2O уe – volumetric density of rocks of the screen , tf./ c.m he – thickness of the protection screen ,m

Should the relation eea hP ⋅γ≤⋅γ be not reached, there have to be implemented several measures among which the construction of an internal dump with advance bench from a certain elevation and which slope will maintain a certain distance up to the slope of the deposit under mining.

Currently, in practice, if there is a non-homogenous protection screen, the admissible pressure is calculated based on the relation:

ee h8,0P ⋅γ⋅= , fig 10.

Fig.10 Variation of the admissible pressure (Pa) of the screen depending on the its thickness within the meadow zone

1 - Pa =1,2 γehe; 2 - Pa =γehe; 3 - Pa =0,8 γehe

For the hilly zones, where lignite layers are more inclined than in the meadow zone the following relation for the admissible pressure calculation is recommended :

ee2

2e

ia h2,1bh

2P ⋅γ⋅+⋅σ⋅= (m col H2O)

where: σ is the rock stretching resistance , tf/ sq.m b- width of the trench base

The correlation between the two parameters of the above relation can be seen in fig 11.

Fig. 11 Variation of the admissible pressure (Pa) on the screen depending on its thickness ( he) in the hilly zone

20


The opening of the floor (distance between the two slopes) can be easily determined based on the known relations from the material resistance.

The screen is considered as an encapsulated beam – on one side below the deposit and on the other side below the dump. Due to the pressure evenly distributed from the floor, there will be an evenly distributed stress on the beam throughout the opening.

The maximum bending moment Mîmax will be carried out in the two encapsulated supports and is given by the relation:

12bLpM

2

maxi⋅⋅

= or

12bL)hP(

M2

eemaxi

⋅⋅γ−= (tm)

where: ee hPp ⋅γ−= is the uniformly distributed load where: P = pressure at the floor, t/sq.m L- floor opening, m; b- beam width , m

Knowing that the resistance module is given by the relations:

i

maxiMW

σ= and

6hb

W2e⋅

= (m3)

it can be written :

i

2ee

i

maxi2e

12bL)hP(M

6hb

σ⋅⋅⋅⋅γ−

=σ

=⋅

i

2ee

2e

12bL)hP(

6hb

σ⋅⋅⋅⋅γ−

=⋅ from where:

ee

i2e2

hPh2

L⋅γ−σ⋅⋅

= (m2)

ee

i2e

hPh2

L⋅γ−σ⋅⋅

= (m)

where besides the other known notations σi ( tf/ sq.m) represents the breakage resistance at rock stretching of the open cast floor.

Most times the admissible width of “L”floor is determined based on the practice data. It varies between 50 and 100 m.

Based on the above reasoning the thickness of the protection screen for a certain floor pressure can be calculated :

i

2ee

2e

12bL)hP(

6hb

σ⋅⋅⋅⋅γ−

=⋅

bLhbLPhb2 2ee

22ei ⋅⋅⋅γ−⋅⋅=⋅⋅σ⋅

0bLPbLhhb2 22ee

2ei =⋅⋅−⋅⋅⋅γ+⋅⋅σ⋅

b4LPb24bLLb

hi

22i

242e

2e

e ⋅σ⋅

⋅⋅⋅σ⋅⋅+⋅⋅γ±⋅⋅γ−=

b4bLP8LbL

hi

2i

22e

e ⋅σ⋅

⋅⋅γ−⋅σ⋅+⋅γ⋅= ∈

i

i22

ee 4

)LP8L(Lh

σ⋅

⋅γ−⋅σ⋅+⋅γ= ∈ (m)

Calculation model of the protection screen. Stress condition and deformations of the protection screen

Based on the method the ABCD fig. 12

protection screen is actually working, it can be assimilated to an encapsulated plate loaded with a uniformly distributed load equal to the hydrostatic pressure of the aquiferous.

Fig 12. Sizing of the protection screen

To work out this issue, it is first consider the stress of the screen as a plate simply leaning on a the contour , loaded with a load uniformly distributed throughout the surface and then it is considered a plate loaded with bending moments on the contour, resulting at the distributed load and by overlapping the impacts, the real case result.

The maximum stress of the protection screen. Based on the relations established for the

cutting forces and bending moment expressions, the stress diagrams can be drawn up, fig 13.

21


Fig.13 Stress diagram and bending moments for the short side of the screen

The stress diagram shows that the maximum absolute values of the protection screen stress occur in the encasing sectors where Txmax = 0,5· p·L and Mxmax = 0,0833·p·L2. It partly justifies the fact that some papers consider that the protection screen gets broken because of the shearing in encapsulation .

Actually, it is about a stress consisting of unitary efforts:

h2Lp

hLp5,0

AT maxx

max⋅

=⋅⋅

==τ

2

2

2

2

z

maxxmax

h2Lp

hLp0833,06

WM

⋅

⋅≈

⋅⋅⋅==σ

where: 6hbW

2

z⋅

= ;

if b=1 it results6

hW2

z =

A and Wz representing the area and respectively the bending resistance module of a plate with unitary width and thickness, h.

Taking into account that for the considered case:

α⋅⋅γ−⋅γ= coshHp 0 where : γ is the volumetric density of rocks γ0 – specific density of water H – hydrostatic pressure at the protection screen base β – inclination angle of the screen against the horizontal line, then the above relations become:

h2L)coshH( 0

max⋅β⋅⋅γ−⋅γ

=τ

2

20

maxh2

L)coshH(⋅

⋅β⋅⋅γ−⋅γ=σ

If we accept as criteria for reaching the stress limit condition, the admissible limit at stretching or compression σ of the material of the protection screen and applying the theory of the maximum tangential unitary stresses then the admissible hydrostatic pressure at the horizontal screen base (β=0) is determined as follows:

2max

2maxa 4 τ⋅+σ≥σ

2

e

2

2e

2

a h2Lp4

h2Lp

⎟⎟⎠

⎞⎜⎜⎝

⎛⋅⋅

+⎟⎟⎠

⎞⎜⎜⎝

⎛

⋅

⋅≥σ

4hL

h2Lp

2

eea +⎟⎟

⎠

⎞⎜⎜⎝

⎛⋅⋅

≥σ

of which at the end, there is obtained:

2e

2

a2

h4LL

h2p

⋅+⋅

σ⋅⋅=

β⋅⋅γ−⋅γ= coshHp ee0 for β =0

ee0 hHp ⋅γ−⋅γ=

2e

2

a2e

ee0h4LL

h2hH

⋅+⋅

σ⋅⋅=⋅γ−⋅γ

2e

20

a2e

0

ee

h4LL

h2hH

⋅+⋅⋅γ

σ⋅⋅+

γ⋅γ

=

For a certain screen, giving different values of L there is obtained the correlation between the two parameters.

The laboratory determinations on models and practical observations throughout the years in the lignite open casts concluded that the floor opening has not a significant impact on the value of the admissible pressure on the protection screen, fig.14, allowing to ensure a relatively high difference between the coal excavation and the dumping process on an internal dump. In the zones where the protection screens thickness is lower special working measures are required as follows: - excavation and dumping equipments from the last bench will not move on the opened screen ( stripped) but on the working sub-benches; - by means of monitoring hydrotechnical drill holes there will be monitored the variations of the aquiferous zone pressure and thus, the required measures can be taken to reduce it;

22


- infill drilling for stress removal to maintain the hydrostatic level at admissible values; - the floor opening will be maximum 50m, and the open cast floor will be covered by drains or filtering bed consisting of ballast and 50-60 cm thick;

- under special conditions when the screen thickness is low, useful mineral benches will be left on the open cast floor and thus the difference between the face and dump is reduced.

Fig 14. Correlation between the opening of the open cast floor and the admissible pressure on the protection screen

Finally, we conclude indicating that the measures taken on the work site for reducing the artesian horizon pressure on the protection screen and the technological process operation determined that the economic activity developed throughout the years was profitable and safe. References 1. Băican, G. Contribuţii la dezvoltarea tehnologiilor de exploatare a stratelor de lignit situate în condiţii hidrogeologice grele. Teză de doctorat, Universitatea din Petroşani, 1998.

2. Fodor, D., Rotunjanu, I., Băican, G. Influenţa activităţii miniere din regiunea Olteniei asupra resurselor şi calităţii apelor subterane. Revista Minelor nr.1/1996. 3. Fodor, D. Exploatarea zăcămintelor de minerale şi roci utile prin lucrările la zi. Ed. Tehnică Bucureşti, 1995. 4. Fodor, D., Băican, G. Detensionarea orizontului acvifer captiv prin aplicarea forajelor cu erupţie liberă în Bazinul Minier Rovinari. Revista Minelor nr.10/2010. 5. Poboran, V., Gonteanu, Z., Matei, I. Dimensionarea treptelor de haldă interioară la I.M.Rovinari. Revista Minelor nr.2/1964.

23


NEW PROFILE FUNCTION FOR GROUND SUBSIDENCE ASSESSMENT IN THE CASE OF UNDERGROUND COAL MINING

Dacian MARIAN*, Ilie ONICA**, Eugen COZMA**

The Petroşani Hard Coal Basin of Romania

contains a balance reserve of about one billion tonnes of coal. After the year 1990, in conformity with the new demands of the market economy, the coal production of this basin was reduced to about 3.5 million tonnes per year. In these conditions has arisen the necessity of revaluation of the impact produced by the underground mining on the ground surface; to determine the development of the subsidence phenomenon in view to elaborate some of the prevention methodologies and the design of the safety pillars for some objectives situated on the surface and underground. Therefore, besides starting the new subsidence and displacement measurements, in the first stage, we proceeded to analyse the old measurements achieved at the Hard Coal Company level, along the time, in different mining fields. Having in view the great diversity of the geo-mining conditions of the mined zones (thick coal seams with gentle and great dip, situated at the variable depths), the most significant cases were taken in study. After the analysis of these measurements, it was elaborated a special time dependent profile function for the conditions of gentle and medium dip seams, as Uricani mine, and generalized for the great dip mines, as Vulcan, Lonea, Petrila, Dâlja mines, with a very good precision of the results. Also, for all these mines, was modified the profile function elaborated by Peng and Chen [22] for Northern Appalachian Coalfield, taking into account the time factor. Keywords: subsidence, displacement, profile function, finite element method Jiu Valley hard coal basin

The Petroşani Hard Coal Basin contains the most important hard coal deposit of Romania, with a balance reserve of about one billion tonnes of coal. This coal deposit was known and mined since the year 1788, as far back as the Austro-Hungarian Empire [1]. But, the intensive coal mining of this deposit began at the same time with Romania’s industrialisation, after the Second World War, reaching after 1980 over 9-10 millions tonnes of coal per year [1], [23]. Due to Romanian industry reorganisation, after the year 1990, in conformity with the new demands ____________________________________ *Ph.D eng. University of Petroşani **Prof.eng. Ph.D University of Petroşani

of the market economy, the coal production of this basin was reduced to about 3.5 million tonnes per year.

From the beginning this coal deposit was split into 16 mining fields, from which following several successive reorganisation and closing stages, only 7 mining fields are left in activity.

The complicated deposit tectonics determines the delimitation in geological blocks of reduced extent (most of them varying between 200 and 300 m) and an equally technical difficulty in mining. Moreover, there occurs a methane gas emission (of over 10 to 15 methane m3/coal tonne) and there is a marked tendency of coal self-ignition [1], [23].

In this coal basin, through the geological research works, there was identified a number of 18 coal seams, of which the most economical importance having the coal seam no.3 (48%) and coal seam no.5 (12%).

The sedimentary rocks complex, in which these coal seams are present, consists in rocks deposits which belong to Superior Cretaceous, Neocene and the Quaternary [23].

As the deposit genesis is sedimentary, the most frequent rocks in the basin are: limestones, marls, argillaceous or marly sandstones, conglomerates, etc., their strength ranging between 15–16 MPa up 50–60 MPa, sometimes even more. Mainly, they are rocks of relatively low stability [4], [16], [25].

The subject of this study consists in the underground mining influence analysis on the ground surface of the coal seam no.3 in the case Uricani, Vulcan, Lonea, Petrila and Dâlja mines, by using a newly developed profile function. Profile functions

Subsidence is an inevitable consequence of

underground mining – it may be small and localized or extend over large area, it may be immediate or delayed for many years. Mine subsidence may be defined as ground movements that occur due to the collapse of the overlying strata into mine voids [24].

The subsidence consists of following major components: subsidence, displacement, slope, curvature and horizontal strain. Also, there are several terminologies that used to define the characteristics of a subsidence profile in a major cross section: angle of draw, angle of critical deformation, angle of break, inflection point and radius of major influence [21].

24


The factors controlling the final surface deformations are the following: physical properties of the overburden strata, size of opening or gob, mining depth (mining depth and mining height, mining depth and mining width), multiple panel mining, surface topography, time elapse [21], near-surface geology, geologic discontinuities, fractures and lineaments, groundwater, water level elevation and fluctuations, method of working, rate of face advance, backfilling of the gob, etc [24].

The major objectives of the subsidence engineering are: 1) prediction of the ground movements; 2) determining the effects of such movements on structures and renewable resources; 3) minimizing damage due to subsidence [24].

Existing subsidence prediction techniques fall under two basic categories, empirical and phenomenological. Promising empirical methods for prediction of the subsidence over underground mines consist of the following: 1) graphical; 2) profile functions; 3) influence functions. Profile functions involve the derivation of a mathematical function that can be used to plot a complete profile of the subsidence trough at the surface. It differs from a phenomenological approach in that the constraints employed in the profile function are empirically derived from observed data [24].

This method can be readily applied to geologically dissimilar conditions by modifying the constant values. Profile functions nave been successfully applied in several countries such: Poland, Hungary, Soviet Union, and United State etc. [24] and actually in Romania. The example of profile functions are the following [24]: A) Critical extraction: -Hyperbolic profile function: UK [6], [27]

( ) ⎥⎦

⎤⎢⎣

⎡⎟⎠⎞

⎜⎝⎛ ⋅

−⋅⋅=B

xcWxW tanh121

max (1)

-Error profile function: Poland/Upper Silesia [7]

( ) ( )⎭⎬⎫

⎩⎨⎧

⎥⎦⎤

⎢⎣⎡

∫ ⋅−−⋅⋅= Bx duuWxW /ln0

22/1max exp21

21

π(2)

-Exponential profile function: Hungary [10], [11]

( ) ( )⎥⎥⎦

⎤

⎢⎢⎣

⎡ +⋅⎟⎠⎞

⎜⎝⎛−⋅= 2

2

max 21exp

BBxWxW (3)

US/Appalachia [22]

( )⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎠⎞

⎜⎝⎛ ⋅

−⋅=d

BxcWxW expmax (4)

-Trigonometric profile function: USSR/Donets, General Institute of Mine Surveying [2]

( ) ⎥⎦

⎤⎢⎣

⎡⎟⎠⎞

⎜⎝⎛ ⋅

⋅⎟⎠⎞

⎜⎝⎛−⎟

⎠⎞

⎜⎝⎛−⋅⋅=

Bx

BxWxW π

πsin11

21

max (5)

Hoffman [5]

( ) ⎥⎦

⎤⎢⎣

⎡⎟⎠⎞

⎜⎝⎛ −⋅⎟

⎠⎞

⎜⎝⎛⋅= 1

4sin2

max BxWxW π

(6)

B) Subcritical extraction: -Trigonometric profile function: USSR/Donets, General Institute of Mine Surveying [2]

( ) ( ) ⎥⎦

⎤⎢⎣

⎡⋅

−+⋅⋅= 2

222/1

21max 41, BnAnnnWxW (7)

where:

⎟⎠⎞

⎜⎝⎛

⋅⋅⋅

+−=ππ

22sin1 xxA

( )xB ⋅+= πcos1 -Hyperbolic profile function:

Poland/Upper Silesia [8], [26]

( ) ( )⎥⎦⎤

⎢⎣⎡ ⋅

−+⋅

⋅⋅=B

xB

wxWxW 2tanh2tanh21

max (8)

Where: x is horizontal distance; c - arbitrary constant; B - radius of critical area of excavation; u - integration variable; w - panel width; W(x) – profile function; Wmax - maximum possible subsidence; n1, n2 – coefficients related to width/depth; n – n1 or n2 depending on side of panel.

Subsidence analysis in the case of the coal seam no.3, block v, panel 1, Uricani mine

The ground surface displacement and deformation monitoring under the underground mining influence at the Uricani Mine is achieved by the medium of the monitoring station composed of 10 observation benchmarks (the station length is of 563.6m).

The topographical measurements were three in three months, beginning with October 2007. This monitoring station provides data concerning the ground surface displacements and deformations by consequence of the underground mining of the coal seam no.3, block V, panel 1 (Fig.1).

25


Fig.1. Monitoring station for the ground surface

subsidence at the Uricani Mine

The mining of the thick and gentle inclined coal seam (of under 10o) was achieved with top coal caving longwall mining (with a length of 90m) on the entire seam thickness and on the panel length of 354m. This panel mining began in 2003 and was completed in the second half of the year 2007.

Besides the horizontal displacement U, in mm, and the horizontal strain ε , in mm/m, other important parameters which define the subsidence basin are: the subsidence or the vertical displacement, W, in mm; slope, T, in mm/m; curvature, K, in m-1 [14].

Studying these parameters, we found that between them there exist some dependencies, namely: the vertical displacements are maximum when the slope is zero and presents an inflexion point for a maximum value of the slope (in the point where the curvature of the subsidence basin vanishes).

For a mathematical expression of these dependencies, the following functions will be defined: W(x) is the vertical displacements function; T(x) – slope function; K(x) – curvature function.

Thus, the measured subsidence basins were statistically analysed [12], [15] with the aid of a

new developed profile function which has the following form [9]:

xcb exaxW ⋅−⋅⋅=)( (9) Where: a, b and c are the regression

coefficients. Between these functions exists the followings

mathematical correlations, namely [14]:

( ) ( ) 2

2;

dxWdxK

dxdWxT == (10)

Taking into account the previous correlations, depending on the regression parameters, there could be established the other parameters’ equations of the subsidence basin.

)()()()1(

xcbexa

dxxdWxT xc

b⋅−⋅

⋅==

⋅

−

(11)

For 0)()( ==dx

xdWxT , respectively at the

distance cbx = results the maximum subsidence:

bb

ecbaW −⋅⎟⎠⎞

⎜⎝⎛⋅=max (12)

Also, the curvature function of the subsidence basin is:

Aexadx

xWdxK xcb ⋅⋅⋅== ⋅−− )2(2

2 )()( (13)

Where: ⎥⎥⎦

⎤

⎢⎢⎣

⎡−⎟

⎠⎞

⎜⎝⎛ −⋅= b

cbxcA

22

The inflexion points x1 and x2 of the vertical displacement curve (for 0)( =xK ) are:

cbbx ∓

=2,1

In the case of the coal seam no.3, block V, panel 1, Uricani Mine, the coefficients a, b and c obtained for every partial subsidence profile and the square of the coefficient of determination R2 of every equation (9) are presented in Table 1.

Tab. 1. Regression coefficients a, b and c and the coefficient of determination R2

Data Time – t [month] a b c R2

03.12.2007 1.25 -30104.201⋅ 14.784333 0.041864 0.984 15.03.2008 4.6 -23106.279 ⋅ 11.414900 0.032404 0.986 16.06.2008 7.7 -19102.494 ⋅ 9.696927 0.026632 0.985 05.09.2008 10.3 -15101.858 ⋅ 7.950222 0.022357 0.985 15.11.2008 12.7 -14101.152 ⋅ 7.592713 0.021372 0.983 12.03.2009 16.5 -14101.041⋅ 7.637613 0.021582 0.968 12.06.2009 19.5 -14102.522 ⋅ 7.460140 0.020980 0.961 15.09.2009 22.7 -14107.914 ⋅ 7.247970 0.020503 0.956

26


To introduce the time variable into this profile function, the regression operation of the all regression coefficients, shown in the Table 1, was made, depending on the time t. Thus, there resulted a new generalized profile function, time dependent, which has the form [9]:

xctcbtba extatxW ⋅+⋅−+⋅ ⋅⋅⋅= ))ln(()ln(1

21212),( (14) where: x is the distance measured from the limit of the subsidence basin; t–time;

0074.0;593.2;102 1131

1 −=−=⋅= − cba ; 0435.0;365.15;936.12 222 === cba (R2=0.971)

are the regression coefficients of the generalized profile function.

The real subsidence curves, depending on the time, and the results of the time dependent profile function are presented in Figure 2.

-20

0

20

40

60

80

100

120

140

160

180

0 100 200 300 400 500 600 700 800 900 1000

Distance - x (m)

Subs

iden

ce -

W (m

m)

MeasuredRegression

Fig. 2. Real curves of the ground subsidence and the corresponding profile functions, in the case of the coal seam no.3, block V, panel 1, Uricani Mine

In the year 1981, Peng and Chen [21], [22]

developed the following negative exponential function of the subsidence profile on the major cross section of the subsidence basin:

AWxW ⋅= max)( (15)

Where: bzaeA ⋅−= ; Wmax is the maximum

subsidence; a, b are constants; sxz = ; x is the

horizontal distance from the origin (which is located at the centre of the subsidence profile); s is the half-width of the subsidence basin.

Also, for the calculus of the horizontal displacement, the following relation is proposed:

')( max AUxU ⋅= (16)

where: AzbaA b ⋅⋅⋅−= − )1(' . In our cases (when the subsidence profiles are

asymmetrical), in order to obtain the complete subsidence profile, the relation (15) must be applied twice, for the left side and for the right side of the measured subsidence profile. If this relation is applied for every time profile, there will be obtained the corresponding regression coefficients as and bs, for the left side profile, and ad and bd for the right side profile. Similar to the profile function (14), so as to introduce the time variable in the Peng & Chen function, the regression of the

regression coefficients was made, depending on the time. Thus, the following relations were obtained: a) – for the left side of the subsidence profile [9]:

sns zm

s eWtxW ⋅−⋅= max),( (17) where: 21 )ln( sss atam +⋅= and

21 )ln( sss btbn +⋅= The obtained regression coefficients are the

following: 139.2;074.0;642.6;936.0 2121 =−==−= ssss bbaa

(R2=0.994) b)– for the right side of the subsidence profile [9]:

dnd zm

d eWtxW ⋅−⋅= max),( (18) where: 2

1da

dd tam ⋅= and 21

dbdd tbn ⋅=

For the geo-mining conditions of the Uricani mine, the regression coefficients have the following values:

;693.0;964.6 21 −== dd aa 401.0;085.4 21 −== dd bb (R2=0.983)

The real subsidence curves, depending on the time, and the approximation results of the modified Peng & Chen time dependent profile function are presented in Figure 3.

27


-20

0

20

40

60

80

100

120

140

160

180

0 100 200 300 400 500 600

Distance - x (m)

Sub

side

nce

- W (m

m)

Measured Peng&Chen modified - Left Peng&Chen modified - Right Fig.3. Real subsidence curves and the curves of the Peng & Chen modified profile function

In the previous figure, there could be observed

that the Peng & Chen modified relation offers a very good fit of the measured data. The main advantage of this profile function is that it takes into consideration both the maximum subsidence and the time. In the case of deficiencies, it may be mentioned that: if the monitoring station didn’t cover the entire profile of the subsidence basin, the function couldn’t predict the behaviour of the entire subsidence profile; the connexion between every

time dependent left and right profiles is through an angular point.

The subsidence basin of the 2D finite element numerical model [9], [13], [17], [18], [19] in the Mohr-Coulomb elasto-plastic behaviour hypothesis, was compared with measured subsidence (Fig.4), resulting an equal maximum subsidence but with certain deviation from the general subsidence profile.

-20

0

20

40

60

80

100

120

140

160

180

200

0 200 400 600 800 1000 1200 1400

Distance - x (m)

Subs

iden

ce -

W (m

m)

Measured 03.12.2008 Measured 15.03.2008 Measured 16.06.2008 Measured 05.09.2008Measured 15.11.2008 Measured 12.03.2009 Measured 12.06.2009 Measured 15.09.2009Subsidence - 2D FEM Modelling Subsidence - 3D FEM Modelling

Fig. 4. Subsidence basin obtained from the numerical modelling compared with the real measured subsidence profiles

For to achieve the 2D and 3D analysis of the

ground surface stability, affected by the underground mining of thick coal seam no.3, panel 1, block V, at the Uricani Mine, was used CESAR-LCPC computational code [9], [13], [17], [18], [19]. Thus, for 3D analysis a single model was created, with “mining voids”, in the hypothesis of the elastic behaviour of the rock massive [9].

The subsidence basin obtained by the numerical modelling, in elasticity, with 3D finite elements,

following the ground surface monitoring station trail (Fig.1) is shown in figure 4, in comparison with the measured subsidence and the results from the 2D numerical modelling (in the principal profile).

Also, in figure 5 is represented the variation of the horizontal displacements after X axis and in figure 6, after Y axis (transversal on the monitoring station).

28


-60

-40

-20

0

20

40

60

0 200 400 600 800 1000 1200 1400

Distance - x (m)

Dis

plac

emen

t alo

ng th

e X

dire

ctio

nu

(mm

)

Fig.5. Horizontal displacements after X axis, obtained from 3D numerical modelling

-8

-6

-4

-2

0

2

4

6

8

10

12

14

16

0 200 400 600 800 1000 1200 1400

Distance - x (m)

Dis

plac

emen

t alo

ng th

e Y

dire

ctio

nv

(mm

)

Fig.6. Horizontal displacements after Y axis, obtained from 3D finite element numerical modelling

(transversal on the monitoring station)

Subsidence analysis in the case of the coal seam no.3, block VII-VIII, face no. 366 and 376, Vulcan Mine

The monitoring of the ground surface subsidence under the influence of underground mining at the Vulcan Mine is made by aid of the monitoring station composed of 16 benchmarks (the total length of the monitoring station being of 620.8m). The topographical observations were executed in a number of three in three months, beginning with October 2008. This monitoring station provides the data concerning the ground surface subsidence and deformation data as a consequence of the underground mining of coal seam no.3, block VII-VIII, faces no. 366 and 376 (Fig.7).

Coal seam no.3 (with an average thickness of about 50m) is mined in horizontal slices with top coal caving mining method, related with these two coal faces. The mining began in 1964, when the roof control by rocks caving was used.

After the statistical analysis of the measurements and the approximation of these with the aid of the profile function (9), then after the regression operation of the regression coefficients of every measurement stage, the generalized profile function (14) was obtained, time dependent, with the following regression coefficients:

;0113.0;1863.4;107 11132

1 −=−=⋅= − cba1363.0;35.60;23.21 222 === cba (R2=0.950).

Fig.7. Vertical cross - section, Vulcan Mine

29


The subsidence curves, periodically measured, as well as the approximation curves of the time dependent profile function is graphically

represented in Figure 8, where it is shown a very good fit of the in situ measurements.

-200

0

200

400

600

800

1000

1200

1400

1600

1800

0 100 200 300 400 500 600 700 800

Distance - x (m)

Subs

iden

ce -

W (m

m)

Measured

Regression Fig.8. Real subsidence curves and the curves of the time dependent profile function,

in the case of coal seam no.3, block VII-VIII, face no.336 and 376, Vulcan Mine Subsidence analysis in the case of the coal seam no.3 and 5, block VI, Lonea Mine

Hereinafter, the measurement achieved on an old monitoring station will be analysed, materialized in the year 1985 by the Mining Faculty of Petroşani. This station is composed of two alignments: one strike alignment with a single stable end composed of 14 benchmarks (with a total length about 380m) and one transversal alignment with a single stable end, composed of 35 benchmarks (with a total length about 558m). The strike alignment was monitored until the year 1987, when the stable benchmark was lost and on the strike alignment the observation was made until the year 1996.

This monitoring station provides the data concerning the ground subsidence as effect of the mining of coal seam no.3 and 5, block VI (Fig. 9). The average dip of the coal seams is of about 30o and the thickness is 28-42m, for the coal seam no.3 and 4-5m, for coal seam no.5. The applied mining method is in horizontal slices, with roof control by integral rocks caving [3].

Similarly with the previous cases, the regression coefficients of the generalized time dependent profile function (14) are the following:

;013716.0;527.8;103 11123

1 −=−=⋅= − cba 095607.0;017.54;949.46 222 === cba

(R2=0.970).

Fig. 9. Transversal cross-section trough the coal deposit of the Lonea Mine

30


Also in this case, it is observed a good statistical approximation of the real measurements with this profile function.

The subsidence curves, in time measured, as well as the statistical approximation with the generalized profile function (14) are graphically represented in Figure 10.

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

0 100 200 300 400 500 600 700 800 900 1000

Distance - x (m)

Subs

iden

ce -

W (m

m)

Measured

Regression Fig. 10. Subsidence curves, time dependent, measured and approximated with the profile function,

for the case of coal seam no.3 and 5, block VI, Lonea Mine

As it is shown in Figure 10, because of the advancement in the deep of the mining of coal deposit, the position of the point, corresponding to the maximum subsidence, for every intermediary subsidence profile, is modified and the subsidence basin develops asymmetrically, and more laterally. Subsidence analysis in the case of the coal seam no.3, face no. 138 and 139, Petrila Mine

The measurements made along the alignment 200, materialized in year 1981, are composed of 16 monitoring benchmarks, disposed on the distance of 250m. Since 1978, the coal seam no.3 mining, under the level +300m, was practiced by slices,

using the roof control by caving at the area of face no. 138 and 139. During the year 1991, in the face no.139 was achieved the total filling at the level +200m [20].

Similar with the previous cases, the statistical analysis of the measurements was made by profile function (9) and the generalized time dependent function (14) which led to the following regression coefficients:

;002496,0;364,0;10686,2 114

1 −=−=⋅= − cba019876,0;828,2;414,2 222 === cba (R2=0.981).

The subsidence curves of the real data and the results of the profile function, defined by the previous coefficients, are represented in Figure 11.

0

100

200

300

400

500

600

700

800

900

1000

1100

0 50 100 150 200 250 300 350 400 450 500

Distance - x (m)

Subs

iden

ce -

W (m

m)

Measured

Regression Fig.11. Subsidence curves of the measured and approximated values,

for the case of coal seam no.3, face no. 138 and 139, Petrila Mine

31


Subsidence analysis in the case of the coal seam no.3, block III, Dâlja Mine

In this case it will be analysed the measurement achieved on a monitoring station that was materialized in the year 1975, composed of a transversal alignment with two stable ends, involving 33 benchmarks, along a distance of 841.8m.

The observations, on this monitoring station, were made biannually, until 1981. This station had the role of observing the ground subsidence and displacements caused by the underground mining of coal seam no.3, block III, mined in horizontal slices and roof control by rocks caving [3]. In this

block the coal seam no.3 has the thickness ranging between 2 and 11m and the dip of about 60 – 68o [20].

As in the cases previous presented, the statistical analysis led to the profile function (14), explicit in function of the time, with the aid of the following regression coefficients:

;024739.0;879.11;10860.3 11140

1 −=−=⋅= − cba135407.0;180.63;418.62 222 === cba ;

(R2=0.865). The subsidence curves, measured and

approximated, are shown in Figure 12.

0

500

1000

1500

2000

2500

3000

3500

4000

0 100 200 300 400 500 600 700 800

Distance - x (m)

Subs

iden

ce -

W (m

m)

Measured

Regression Fig. 12. Subsidence curves, depending on the time, in the case of coal seam no.3, block III, Dâlja Mine

Conclusions

At the same time with the reconsideration of

the mining of Jiu Valley hard coal deposit, because of the closing programme of several mines and the beginning of a new panels’ mining and the need for the revalorization of the surface lands and the assessment of the constructions’ integrity, the requirement of assessment of the ground surface stability has arisen, in the mining fields influence areas.

Therefore, an immediate assessment of the measurements provided over time was tried, in the different Jiu Valley mining fields and the analysis of this data base, stored by the Hard Coal Company of Petroşani (some significant case studies are presented in this paper).

We mention that the data analysis was difficult because the ground surface monitoring was made following the alignments that were not always relevant from a scientific point of view. Over time,

the purpose of this monitoring was to observe the stability of certain roads, land areas and other targets of immediate interest.

By consequence, a time dependent profile function was elaborated, which predicts very well the development in time of the subsidence basins produced as an effect of the underground mining of the thick coal seams of the Jiu Valley coal basin. Also, with the encouraging results, we tried to adapt, at the Jiu Valley conditions, the profile function made by Peng and Chen for the Northern Appalachian Coalfield.

The subsidence phenomenon analysis by the profile functions methods, by numerical modelling and other researches tools will be further developed, at the entire coal basin level. These are the prediction and control methods, necessary for the new panels mining design and the measures required to mitigate the degradation phenomenon of the lands situated under the influence areas of the underground mining fields.

32


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19. Onica, I., Cozma, E., Marian, D. Analysis of the Ground Surface Subsidence in the Jiu Vally Coal Basin by Using the Finite Element Method, Proceedings of 11th International Multidisciplinary Scientific Geo-Conference & EXPO SGEM 2011, Modern Management of Mine Producing, Geology and Environmental Protection, Albena, Bulgaria, 19.06.2011- 25.06.2011.

20. Ortelecan, M. Studiul deplasării suprafeţei sub influenţa exploatării subterane a zăcămintelor din Valea Jiului, zona estică, Teză de doctorat, Universitatea din Petroşani, 1997, 195p.

21 Peng, S.S. Coal Mine Ground Control, John Wiley and Sons, New York, 1986, pp. 420-460.

22. Peng, S.S., Chen, D.W. Analysis of Surface Subsidence Parameters Due to Underground Longwall Mining in the Northern Appalachian Coalfield, Department of Mining Engineering, West Virginia University, 1981, TR 81-1, 22p.

23. Petrescu, I., ş.a. Geologia zăcămintelor de cărbuni, Editura Tehnică, Bucureşti, 1987, pp.81-106.

24. Singh, M.M. Mine Subsidence (Chapter 10.6), in SME Mining Engineering Handbook, SME, 1992, pp. 938-971

25. Todorescu, A. Proprietăţile rocilor, Editura Tehnică, Bucureşti, 1984, 676 p.

26. Wardell, K., Webster, N.E. Some Surface Observations and Their Relationship to Movements, Leeds, England, 1957, pp.141-148.

27. Wardell, K. Surface Ground Movements Associated With the Total and Partial Extraction of Stratified Mineral Deposits, MSc Thesis, University of Nottingham, UK, 1965.

33


ANTHROPIC IMPACT ASSESSMENT ON THE TRUCTURE AND MORPHOLOGY OF THE EASTERN REGION OF PETROȘANI MINING BASIN

Ciprian NIMARĂ*

Abstract. Mining, the main economic activity

in Petroşani mountain valley, was a vital necessity for the development of the community of this micro-region, but whose "products" could be observed both in the natural and social, political environment. In the natural environment is obvious by the man made morphology which vary by sizes, shapes and morphological processes. The main aim of assessment of anthropic impact on landscape and the identification of areas with affected geomorphological environment, was to be able to find later the necessary solutions for landscape and functional reintegration of the anthropic landscape. Key words: anthropic impact, geomorphological environment, morphology, structure, assessment, region, sector. Introduction

As a result of dislocation-relocation and storage of mining mass, the original territory is changed in

terms of shape and functionality, the result was the emergence of an anthropic landscape with a high probability of risk appearance.

The areas with coal mining activities are characterized by the presence of anthropogenic morphology with different sizes, various geometrical features, diversity of morphological processes, evolution time, lithological structure, etc.

These anthropic modelling processes are a vital necessity in the technology evolution.

To be more easily to analyze the affected geomorphological environment from Petroşani Depression, I divided the depression, based on geological, geomorphological and economical criteria, in two distinct regions, and each region was divided into sectors [3], as follows:

Eastern Region: Petroşani-Petrila sector (fig 1); Western Region: Aninoasa-Vulcan-Lupeni

sector and Uricani-Câmpu lui Neag sector.

Figure 1. Location of the Eastern Region of Petroşani Depression

(Petroşani-Petrila sector)

Limits In the northern limit of the analyzed region, was

taken into account the tectonic line. Along this, it can be observed an over-riding of crystalline over the deposits series of conglomerate of sedimentary [2]. At the two formations contact, can be observed the line of the split slope, which on the direction ____________________________________ *Ph.D. University of Petroşani

South West-North East goes under the following peaks: Boţonilor Hill (950 m), Red Stone (1192 m), North Cimpa (978 m). Between Petroşani and North of Cimpa, the northern boundary separates the basin from the Sureau Mountains, formed by crystalline and Mesozoic Domain (Jurassic limestones), which takes the form of a steep.

North-Eastern limit, on a small side, is made up by the Rascoala erosion hollow, sunk on the lower course of this river. It seems that, this hollow was a

34


bay of the Miocene Lake, which came into contact with this corner of the basin.

South and South-East Limit separates the Eastern Region of the Petrosani Depression from Parang Mountains. To the South-East of Jiu gullet, the limit passes to the North of Măgura Hill (970 m), crosses the upper course of Salatruc Valley and the middle course of Maleia, continues to the West of Plaiul Godeanu and Cimpa Hill, reaching to Eastern Jiu Valley

upstream of the Cimpa village. The same morphological limit, well expressed in the mountains and valley, is observed between Jieţ - Cimpa; here piedmont is clearly detached from the mountain, coming right out break of slope between the two morphological units (figure 2).

The Western limit of the analyzed area was considered to be the section between Eastern Jiu Valley and Aninoasa River [3].

Figure 2. Transversal section through Eastern Region of Petroşani mountain valley

Anthropic landforms: dumps

The main anthropogenic structure created as a result of coal mining activity in the Eastern Region of the Petroșani Depression are represented by dumps and coal pits. The vast majority of dumps are located on hillsides or along valleys with or without the hydrological regime.

Land storage quotas generally varies from 650 m in the axis of valleys and 750 m on hillsides with slope angle ranges between 6 ° and 35 °.

In some cases, waste dumps were built on areas where they crossed out valleys without permanent

water courses; in periods of rainfall, lakes are being made, which presence could be a risk for the stability of dumps. The infiltrated water into dumps, changes the physical and mechanical properties of materials and of the land base and may give rise to erosion phenomena. It can also produce a hydrostatic pressures and ultimately can cause landslides or plastic and muddy leakage.

The dumps are composed mostly of clays, shales, sandstones, argillaceous sandstone, depending on the lithology of the exploited area (figures 3, 4 and 5).

Figure 3. Type of rocks at E.M. Livezeni Figure 4. Type of rocks at E.M. Lonea

35


Figure 5. Type of rocks at E.M. Petrila-Sud

Land observations led to the finding of the

some essential aspects related to the presence of sterile dumps (the current state of the dumps of Petroşani Depression is shown in table 1). Usually, the areas of occupied land, and the dumps have the following fatures: - the dumps have a non-uniform geometry and are formed in areas with rough terrain; - it hasn't been executed any work before locating the dumps; this works should ensure the soil scraping, appropriate benches, water drainage etc.; - it hasn't been executed any work for leveling the dumps, which often goes to water accumulation.

Under ground coal mining has special repercussions for surface land as well, by causing crashes, declines or crashing in. These phenomena, don't allow the normal usage of land, for the original purposes, and severely affect the constructions in the area.

Processes from the land surface develop depending on the thickness of the layers. Exploiting

the thin layers of small hip causes only the surface subsidence without being affected the crops from the area. For thicker layers, the subsidence is manifested in the form of steps with intense areas of fractures in the line with layers. Other associated phenomena are: formation of springs, drying up wells and formation of permanent lakes on the bottom of subsidence bed [1]. Fractured and unstable land has affected almost 70 individual peasant households, and in some cases have necessitated the evacuation and demolition of residential blocks in the town of Petrila.

The phenomenon of subsidence has a greater magnitude above the undermined beds and near the fissures limit.

As already noted above the undermined beds, the land affected by subsidence was large and the topographic surface is changed, involving in this way, the restrictions regarding the use of the land.

Table 1. Present situation regarding the affected lnad in the Eastern Region

No.

Economic unit Name of dump Area

(ha) Volume

(m³) Technical

status Owner,

administrator1 Mina Petrila Sud Haldă de steril Jieţ Vest 7,53 1.772.000 Rehabilitated CNH Petroşani2 Mina Petrila Sud Haldă de steril Jieţ Puţ 4 1,14 57.000 Rehabilitated CNH Petroşani3 Mina Lonea III Haldă de steril Defor 12,75 2.149.970 Idle Consiliul local

Petrila 4 Mina Taia Haldă aferentă incintei 3 8.400 Idle CNH Petroşani5 Mina Petrila 2 Haldă de steril 2 Est 1,63 388.540 Idle Consiliul local

Petrila 6 Mina Dâlja

Haldă de steril Puţ auxiliar nr.1

1,74 63.000 Idle CNH Petroşani

7 Mina Dâlja Haldă de steril Plan înclinat 1,74 280.000 Idle CNH Petroşani8 Mina Dâlja Haldă de steril Puţ aux. 1+2 8,00 1.270.000 Idle CNH Petroşani9 Mina Dâlja Haldă de steril Tericon

PA 3 1,20 77.500 Idle CNH Petroşani

10 Mina Lonea 1 Haldă de steril Valea lui Ciort

7,19 982.472 Idle Consiliul local Petrila

36


11 Mina Livezeni Sud Haldă de steril Halda aferentă incintei

11,00 54.000 Idle CNH Petroşani

12 Preparaţia Petrila Haldă de steril Ramura I, II, III, IV şi VI

30 5.105.000 Idle Consiliul local Petrila

13 Preparaţia Petrila Haldă de steril Ramura V 19,59 2.802.299 Active CNH Petroşani14 E.M. Lonea Haldă de steril Lonea I 2,10 350.000 Active CNH Petroşani15 E.M. Lonea Haldă de steril Jieţ 0,78 51.000 Active CNH Petroşani16 E.M. Livezeni Haldă de steril P.A nr. 2 - 3

incinta Maleia 2,30 301.792 Active CNH Petroşani

17 E.M. Livezeni Haldă de steril U.P.Livezeni

2,38 427.057 Active CNH Petroşani

Anthropic landforms: coal pits

Another specific situation for mining activity in the Eastern Region and in the Petroşani mining

basin as well, generally, is represented by the existence of derelict coal pits due to uneconomic exploitation (table 2).

Table 2. Features of derelict coal pits from Eastern Region

Name of coal pit Area (ha)

Area of influence (ha)

Cimpa 9,30 0,75 Jieţ Defor 12,56 1,05 Jieţ Vest 6,41 0,50

Relative stability

Anthropic impact assessment on the landforms from the Eastern region

In designing the assessment methods have been taken into account the type of anthropogenic activity, the resulting products, the ability to rehabilitate the degraded land, the exhibition of the original land and the man made one, solar radiation and the level of interest for the original surface.

Three assessment methods have been proposed to assess the anthropic impact on the natural landforms [4, 5], which have been applied later for the entire basin.

Assessment method of geomorphological quality depreciation

According to the value of the quality depreciation, calculated with the ratio:

DC = Rg + D (1)

value which can be found in table 1 (completed by table 2) and comparing this value with the scale of values shown bellow, it is obvious that, for the Eastern Region of Petroşani mountain valley, the most affected by the anthropic activity is the Eastern Jiu meadow from Petrila town (DC=11) and Maleia accumulation piedmont (DC=10) [5].

The scale of values for quality depreciation is: • 0 unaffected geomorphological environment; • 1 - 3 less affected geomorphological environment; • 4 - 6 moderately affected geomorphological environment; • 7 - 10 strongly affected geomorphological environment; • ≥ 10 intense modified geomorphological environment.

Table 3. Assessment matrix for geomorphologic quality depreciation in Eastern Region

No Name of geomorphological resource

Geomorphologicaltype, gR

Diversity of geomorphological

features of interest, D

Quality depreciation,

DC

1 Meadow of Eastern Jiu (Petrila town) 1 10 11

2 Meadow of Eastern Jiu (right bank, Petroşani) 2 1 3

3 Piemontul Dâlja 1 4 5 4 Maleia Piedmont 3 7 10 5 Valea Arsului 1 2 3 6 Ciort’s Valley 1 1 2 7 Defor Valley 1 5 6

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Table 4. Diversity of geomorphological features of interest in the Eastern Region Types of geomorphological elements No. Name of

geomorphological resource

Accumulation forms

Negative landforms (hollows)

Water accumulation (lakes)

Diversity of geomorphological

features, D 1 Meadow of Eastern Jiu

(Petrila) 5 1 4 10

2 Meadow of Eastern Jiu(right bank)

1 0 0 1

3 Dâlja Piedmont 4 0 2 6 4 Maleia Piedmont 4 1 2 7 5 Valea Arsului 1 1 0 2 6 Ciort’s Valley 1 0 0 1 7 Defor Valley 1 3 1 5

Assessment method based on the

relationship surface exhibition - solar radiation

As regards the exhibition of the originally land (before being subject to anthropogenic interference) in the Eastern Region, it is observed that the terrain with Northern exhibition occupies the most significant area (37,76 ha), while the southern areas are the smallest (3 ha) (figure 6).

As a result of anthropogenic interference on morphology, it is seen that the new created surfaces have a Western orientation (23,68 ha), and areas which benefit for a lower sunlight radiation are those with southern orientation (17, 66 ha) (figure 7). Creditworthiness for the original land were 2, due to the predominantly Northern exhibition, and 6 for areas created by human activity, due to the predominantly Western exhibition [4].

Figure 6. Exhibition of original land Figure 7. Exhibition of anthropic land

Assessment method “alteration – reuse”

After using this assessment method, by calculating the anthropic impact using the ratio:

MR = sN · aT · R (2) and comparing the obtained value with the following scale of values: • 0 – unaffected geomorphological environment, no human intervention, natural environment; • (0 – 25] – less affected geomorphological environment; • (25 – 50] – moderately affected geomorphological environment; • (50 – 100] – strongly affected geomorphological environment;

• (100 – 150] – very strongly affected geomorphological environment due to overall change; it has been obtained values between 11,8 and 67 (table 3) [4]. Comparing the obtained values from table 5 with the scale of values shown above, it can be notice that:

areas with less affected geomorphological environment : meadow of Eastern Jiu (Petroşani – E.M. Livezeni), Valea Arsului and Ciort’s Valley, Dâlja Piedmont;

areas with strongly affected geomorphological environment are : meadow of Eastern Jiu (Petrila), Maleia Piedmont and Defor Valley.

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Table 5. Matrix for human impact assessment on the relief in the Eastern Region

Conclusions

In the Eastern Region of Petroşani mountain valley, the affected geomorphological environment by the mining activity, represent an area of 136,09 ha.

After using the propose assessment methods, it was noticed that the most affected geomorphological resources and those with a very low recovery capacity were: Defor Valley, meadow of Eastern Jiu (near Petrila town) and Maleia accumulation piedmont.

According to the creditworthiness obtained by using the assessment method „exhibition-solar radiation”, (6), comparing it with the value of original land (2), it resulted that the new anthropic land, created by mining activity in the Petroşani-Petrila sector, present a high posibility of recovery in terms of landscape integration.

References 1. Biro, C. Reabilitarea terenurilor degradate de activităţile antropice din bazinul minier Valea Jiului, Teză de doctorat, Petroşani, 2004; 2. Lupu, S. Depresiunea Petroşani, studiu geomorfologic, Teză de doctorat, Facultatea de Geografie, Universitatea Babeş-Bolyai, Cluj Napoca, 1970; 3. Nimară, C. Cercetări privind reintegrarea peisagistică a arealelor afectate antropic din cadrul Bazinului Minier Petroșani, Teză de doctorat, Facultatea de Mine, Universitatea din Petroșani, 2011; 4. Nimară, C. Metode de evaluare a impactului antropic asupra morfostructurii unei regiuni geografice, Revista Minelor, vol. 17, nr. 1/2011

Name of the geomorphological resource

No.

Natural modeling

system

Affected landform

Products of human activity

Strategic level

( sN )

Type of activity

( aT )

Recovery capacity

(%) (R)

Value of the final rate

(MR)

1 Meadow of Eastern Jiu, Petrila

h, a, sb, ci, ps, pt, pec,

dtm

2 6,1 5 (0)

61

2 Meadow of Estern Jiu, Petroşani

(EM Livezeni)

h, sb, ci, pt, 2 2,95 2 (50 – 75)

11,8

3 Dâlja Piedmont h, a, pec, 2 4,7 5 (0)

47

4 Maleia Piedmont h, a, sb, ci, pt, ps, gs

2 5,3 5 (0)

53

5 Valea Arsului h, ps, gs 2 2,85 3 (25 – 50)

17,1

6 Ciort’s Valley h, pt 2 2,65 3 (25 – 50)

15,9

7

Fluvial

Defor Valley h, a, ex, pec,

2 6,7 5 (0)

67

39


THE MANAGEMENT OF AREAS AFFECTED BY MINING INDUSTRY IN THE OLTENIA COALFIELD

Constantin NISTOR*

Abstract The propose paperwork is following to elaborete a aplan of measures for management of grounds afected by minig activities of coal extraction from Oltenia. The study entity is extending between the rivres Olt and Danube and it is hold five basins of coal extraction : Berbesti, Rovinari, Jilt, Motru, Husnicoara, which is concentrated in 13 quarries, and it is affeted till now thousands of hectares of ground. We are focused of surfaces affected of coal extraction in open and underground mines. To touch this target ther is necessary many investigations by using specific methods based on up to data and information. The building of geographyc information sistem is the plan key which will be used during all objetives stages suppling up-to-date information. The data acquisition and actualization from many sources it is a base element into project develop, aspect for this it will be considering very important. Hazard identification and develop scenary of evolution, likelihood evaluation, it is a necesity to identify proplems areas and treatmet measures. Hazard dynamic asses and adjust of measures, depending of process evolution study and information flux is other step. Starting with signalizing afected areas and with potential hazard, it is wants to built a plan of reclaim and find solutions. The solutions need to request land use field before open the mines, economic and social requirement of community. The field reclaim must be done regarding of landscape reinstatement and economic and ecologic functionality to insurance a durable development. Key words: minig management, anthropic relief, susceptibility, hazard, reclaim, rehabilitation

The mining industry has a strong impact on the environment, and its seriousness depends mostly on the extraction methods and the geological conditions (Bell, 2000). The mining activities have an important role in the local and national economy, but when they develop without control they induce a very high risk of soil erosion and severe problems of environment contamination (Coelho, 2007). The mining operations of small or large size are inherently environment destructive and produce large quantities of waste with negative impact on decades (Kitula, 2006). The environment ____________________________________ *Ph.D Asistant University of Bucureşti, Faculty of Geography

problems occur as a result of the inadequate mining and lack of rehabilitation measures. Each mining activity has a potential impact, adverse for the environment, society, culture, health and local communities. Noronha, quoted by Kitula (2006), shows that the social and environment impact is more persuasive in the regions of new communities, where the mines were closed. The mining impact includes local population migration from the ancestral region, disregard and oppressions, as the result of the economic problems. Environmental impact of mining can never be zero, there is always a degree of uncertainty about the type and extension of impact that may arise. Risk Management plays a vital role in development because of inherent adverse consequence, that can’t be eliminated entirely without without turnig the mining into technically or economically non-viable operations (ERM, 2000). Inferior coal mining in the region lying between the valleys Olt and Danube are concentrated in 5 production units: the coal fields Husnicioara, Motru, Jilţ, Rovinari, Alunu and Berbeşti affected over 1 million hectares of land (Fodor, 2002). The influences on the landforms are direct, resulting anthropic landforms, very different from the natural ones, and even man-caused landforms inversions. The lignite quarries are located in hill regions and generate as they extend, real man-made depressions that spread over many kilometers. Given the hill landforms of this region, the only way to place the waste dumps was to put them on the existing negative landforms, along the local small valleys, on the local river beds. Inferior coal exploitation in the region lying between the Olt Valley and Valley Danube is focused in five production units (Fig. 1), coal fields: Husnicioara, Motru, Jilţ, Rovinari, Berbeşti, including 13 quarries and affected over 1 million hectares (Fodor, 2002). The influences on the landforms are direct, resulting anthropogenic landforms, very different from the natural ones, and even man-caused landforms inversions. The lignite quarries are located in hill regions and generate as they extend, real man-made depressions that spread over many kilometers. Given the hill landforms of this region, the only way to place the waste dumps was to put them on the existing negative landforms, along the local small valleys, and on the local river beds of major rivers.

40


Following this sudden change in the landscape area which provides support for all other elements of the landscape, there have been deep changes in the ecological level of the functionality of these reliefs on surfaces. Restoring the original ecological landscape in human personality is almost impossible, since the initial environmental conditions have changed irrevocably, thus seeking to ensure post-closure environmental functionality as close to the original. We believe that a plan for management of degraded land bymining industry is a necessity, to meet requirements for decision making on land management, prevention and community information. Such evaluation and mitigation plans, the impact of mining on the environment from regional and national scale have been made at institutional level in most countries with extractive industry. For example in Slovakia, Environmental Impact Assessment of Mining Activities are still of years "90 part of the Slovak National Monitoring Network (Klukanova, 1999). In France was adopted nationwide Risk Prevention Plans (RPPs) for control risk arising from land movements (Mate 1999, quoted by Merad 2004). This plan provided four types of information: an informative report of the natural phenomena, a hazard map, an evaluation of the situation, and a risk map. Because the evaluation methods based

on a single data source, as the mine position plans, may be incomplete (they are useful only for small surfaces, where the data may be checked on the field), using the multi criteria decision-aid is the preferred approach (Merad 2004). In order to manage properly the regions affected by mining, the U.S. Agency Environmental Protection Agency (EPA) has developed BASINS, (Better Assesment Science Integrating Nonpoint Sources), a specialized software that once installed is able to donwload by itself from various sources, for a selected region all the geographical and geological data, redesign information in a single projection. The program has tools for modeling the affected region and and to calculate the rehabilitation costs. In Australia was developed by the Environmental Protection Agency, ERM (Environmental Risk Management), which is a set of rules and procedures binding measures to prevent environmental risks; they have to be adopted while the mining activity goes on and after that in order to recover the lands affected by mining. This approach has to be systematic and offers considerable benefits, including environment protection performance improvement. We believe that management of degraded lands by mining activities should also include evaluation criteria, prevention focused on the following lines (ERM, 2000).

Fig.1; The repartition of mining activities betwen the arivers Motru and Jiu

41


‐ Procedures and practices to identify hazards ‐ Consequence of these hazards ‐ Estimate the level of risk (quantitative or

qualitative) ‐ Assessing the risk on the basis of relevant and

objective ‐ Decisions about risk minimization and

identification Building a database update is the first step in ensuring an efficient management of land affected by mining activities. Develop methodologies and creation of digital database are time consuming and technically the most difficult part is to make and produce information (Walsby, 2007). In any management activity, the decision is based on information, regarding the operability of its access, interoperability (connectivity with different sources and on different subjects), quality information, updating of information. The only way of collecting and storing information that satisfies those demands is to build a Geographic Information System (GIS), which also offers information for spatial representation (Chacon et. Al. 2006). Under this system can be integrated data of different formats: vector (numeric and alphanumeric, sizes, value, orientation, surface), raster (aerofotograme, satellite images, photos, documents, image synthesis), in different fields: geology, geomorphology, soil, mining, forestry. For efficiency this information can be represented in a single reference system (like Romanian Stereographic System), to enable it more easy integration of topographic data and technical service that is based on the same projection. Building a GIS is based on three areas: direct collection of information from the field by using specific equipment, allowing harvested in vector format (using GPS equipment, GPR, total station, drilling), acquisition of information from different manufacturers or owners (ortofotoplans of the area, satellite images), to collect the geological, topographic and technical date from the extracting units (usually in analog form and converting them into vector format). Information gathering is geared towards field verification and review the information for which there is uncertainty and obtain quantitative information about the presence of certain geomorphological processes (landslides, subsidence, collapse, excess water). In order to evaluate the hazards in the region, we have to collect qualitative information on the intensity and frequency of such processes. Achieving this information implies field and laboratory investigations on the process dynamics and the lithological properties of the affected materials. The field investigations include GPS

mapping at regular periods, using portable equipment and GPS stations. The measurements provided by the total station are difficult to make, but the data on process morphology and dynamics are very accurate. Through the use of new tehnology to collect data are to increase the digital informations which can be process based of new methodologies and emphasize with a biger degrees of accuracy, the areas with potential hazards (Walsby 2007). For this aim we used geology data, the superficial deposits, including anthropogenic deposits classified in terms of geohazard, and there where its exists, validate data with the areas of ocurence. New methods combine the geological knowledges with topographic date and another informations, and each polygon is classified depending on potential of hazard (Walsby 2007). Informaţion about potential hazards were using in making the decisions about the location of civil and industrial buildings, the recovery of grounds affected by mining. Making the necessary core drilling for the extraction of geotechnical analysis, interested primarily numerical parameters that can be modeled to identify the conditions for stability of the process and can be extrapolated to a wider area in the deterministic method. Hazards for which are preconizate experiments on field and laboratory, are specified for affected regions of mining activities, overlapping both the natural and human forms: landslides, subsidences, rockfall, gully. The mining works, always can present a dangers for population and buildings, when pillars and galleries collapse. Such a rupture can cause the surface gradually slight negative movement called subsidence (Merad, 2004). In such a context, hazard and risk assessment tends to be a problem where information is uncertain. Method based on several criteria improves the safety of the finished product. In this approach (Merad, 2004), risk was separated into four classes, class 1 corresponding to the highest degree of risk and the lower class and classify 4 the most down. For the class 1 is enforced a permanent system of monitoring while for the class 4 there are enough topographic investigation. The subsidence resulted from manifestation of pits fall, is transmited on a surface over an area much broader than that occupied by the underground work (Bell, 2000). Subsidence also has a strong impact on groundwater; research on old work (Bell, 2000) showed that about 50% of the water from precipitation infiltrating through the network of surface cracks and then appears in the form of polluted water by a number of small springs.

42


This calls not only reporting areas with underground mining, but also a detailed mapping of areas affected by subsidence and likely to be affected with a real capacity to induce risk both directly and through other hazards (Bell , 2000). G.I.S. data base realized will consitute the sourse of data for to realize simulation to determine the susceptibility of the region to certain process and in the last the identification of area with potential hazards.

Deterministic hazard assessment model is based on identifying factors contributing to their launch. Were identifing three causative factors: geology, topography and water, giving a value of each factor is given by the a set of the relative importance of each type of hazard. These data are then combined, assigning each polygon is a degree of susceptibility and classified by certain rules to form a map of susceptibility to hazards.

The probabilistic model of estimate the susceptibility uses the theories weights of evidencens and fuzy analysis (Bonham-Carter 1989, Klingseisen, 2006, Zahiri et of. 2005), identification of potential areas of occurrence by comparing conditions on a given surface with those of known areas. The difficulty of maps plotting is even higher, becouse in the past, during repeated mappings of industrial location were not specified potential hazard areas and their probability was amplified. Based on areas with different degrees of potential hazard, can be identified anthropogenic objectives (industrial and residential), with varying degrees of vulnerability. Where the degree of vulnerability is the highest will be asses the risk by calculating the potential losses which is exposed property. Study on environmental issues to areas within degraded land due to mining activities are

reflected in the extensive research programs practicality. Devising a methodology applied involves, first, a good knowledge of the structure and functioning of regional geomorphological to identify areas with conflicting state between components. In order to achieve a modern and efficient management of the territory is necessary to achieve a correlation characteristic data chosen, case study experiences on technical measures and rehabilitation of degraded areas within the minerals obtained from countries with experience in this field, such as Germany (Ruhr ) (Bell et al., 2000), United Kingdom, Poland (Silesia Basin), Hungary (Miskolc region), Czech Republic, USA, Australia (Anderson, 2001) etc.. From highlighting areas of hazard and risk assessment, we can move sequentially to a rehabilitation strategy of land affected by mining. It is necessary to lay down the anthropic landscape function to avoid catastrophic effects during or after mining of minerals (Bell 1998, 1999 and Bennett, Doyle 1997). The lack of a management plan and its implementation solutions to reach a situation where land owners have been taken even before the completion of the dump and ensure stabilization measures. Major crops in the early years encouraged to persist, but the lack of productivity in the coming years and occurrence processes leading to land abandonment and their request or the issue of rehabilitation alternatives. How the alternatives are limited due to lack of space, the only measure of rehabilitation in which mining companies were limited reinsurance was to test stability by redistributing the material on the slope without drainage causes.

Fig.2; The micro-open mine Lupoiţa II, where frequently occurs landslides and rock fall

43


Measures envisaged for the rehabilitation plan of the land affected by mining concerns: mapping land affected by mining activities, the overall stability through support strips, drains, storm drain channels, identifying sources of pollution persist represented by technological equipment dismantled and abandoned, the stabilization of the geomorphologies process that undermine the stability of human constructions, reconstruction pedological cover by redistributing soil and providing conditions for their restoration, landscape planning, proposing solutions that combine economic needs with the assurance of stability, the alternating bands of trees with grass and cultivated land areas. Action plan should include measures to halt the development of geomorphological processes, ensuring the functioning of economic land degraded landscape and its reintegration (Ruthrof, 2000). The situation of land affected by mining activities in Oltenia coalfield

For example coal basins from the western part of Oltenia, have large area occupied by small open mine and dumps closed, but unfortunately failed to be reintroduce in agricultural and forestry. In this situation are the quarry: Plostina North, Lupoiţa II, Miculeşti I, Ştiucani, the dumps, Lupoiţa, Ştiucani where mining activities have ceased and the land is in an uncertain situation. Current standards require mines to restore the affected land prior to the commencement stage of economic activities. Either this is not possible, since environmental factors are specific locations that change was irreversible. What is possible and recommended, are the restoration of environmental conditions from the new components: lithology, relief, hydrology, soil, vegetation. For a successful

recovery better land degraded by industrial activities, it is necessary that revaluation plan to start a business there begins by tracking individual components. And since the work on these surfaces is stopped, it is necessary to find alternative solutions that substantially increase the price of work. The mistaken into consideration of each element of the environment, will result in compromising the final result, namely recovery of fertility. In a brief analysis of the environmental components, contained within the perimeters of the affected notes: 1. The lithology, is favorable, being composed by sedimentary rocks (clay, marl, sand, loess, waste coal), with a high degree of corruption, remove the alteration and genesis favorable soil formation. The presence of clay in excess, however, may create problems of instability, the lack of hydrogeological conditions and ensuring adequate slope. 2. The relief is represented by morphology of new man-made land, and must be interpreted three-dimensional by taking into account height and slopes obtained. For the affected areas from Oltenia, morphology waste dumps and abandoned small quarry constitute a problem, because very large slope angle does not guarantee stability of lithology formations. In some areas that small quarry preserve slope of 90 °, which constitute a permanent source of rock fall and landslides. Also the morphology obtained after the modeling process, has to ensure conditions for storm water runoff and drainage water infiltrate in rock mass. In most cases the dumps built in Oltenia not taken into account to create a superficial network of artificial drainage, and to act in the artificial aquifer to drain excess water from anthropogenic reliefs created. These shortcomings have led to the formation of surface water storage areas and water infiltrations onto the clay rock mass with the

Fig.3 Field reclaim by reforestation, a good example for land recover - the dump Roşia Jiu

44


consequent loss of stability. For example you can see the dump Ştiucani, Rogoaze, Monastery Valley, and the small quarry Lupoiţa II. 3. Hydrology, indicate the presence of surface water and in the body dump, necessary to conduct rock alteration processes, pedogenesis and ensure plant physiological functions. The most important is the water contained in the body of new deposits, which should be released gradually to the needs of plants. Or, for this approach, studies are currently not enough and strategies are missing. 4. Anthropogenic soils formed on the surface of the anthropogenic relief shows a skeletal structure, and lack of basal horizons. Because sedimentary rocks, which disintegrate relatively rapidly through physical and chemical processes at the surface to form a thick crust of alteration of approximately 0.5 meters, and in the top an organic horizon A. It was found that the clays and marls from hilly Oltenia contain high levels of phosphorus and potassium, a mineral base to ensure fertility. This leads to improved conditions for crops vegetation pilot of newly formed soils. Unfortunately soils initially present in these regions and were stored in separate heaps, after an interval of 15-20 years have lost their fertility properties and can’t be used to cover the dumps. 5. Vegetation developed on the anthropic landscape is fundamentally different from the spontaneous flora of the region. Due to high productivity on these lands are developed in the first two or three years vigorous vegetation, consisting of less fastidious species. Even crops grown on these surfaces present in the first phase good results. Rapid depletion of soil nutrients and lack of a good structure, creates problems in dry intervals. It is advisable that on these lands to cultivate in the first phase pilot species that contribute to the enrichment of soil in organic matter and support the process of pedogenesis

The above analysis shows that for surfaces where the mining activities have closed, the major problem is the lack of stability and for part of land the legal situation uncertain. Lack of stability may be solved by shaping the morphology of human construction, and reduce slope angles, by designing a superficial stream network and providing conditions for the realization of underground drainage. Uncertainty of land affected by mining is still a touchy subject, from which local communities can’t benefit. In many cases the lands were occupied by former owners undocumented before stopping the mining activities and the introduction in rehabilitation programs.

These fields have been cultivated, the beneficiaries being encouraged byhigher yields from the early years.This has hampered the technical measures of rehabilitation, evry action being considered by the ancient and now the new owners as an abuse. Is the situation of dumps Monastery Valley, Rogoaze, Ştiucani, where former owners have established cultures even beforere moving the equipment. Satisfactory results were obtained in the case of forest plantations. For example the upper part of the the dump Bohore, the small quarry: Porcaşa, North Plostina, Roşia Jiu, where the released land were planted with pseudacacia. Pseudacacia species have adapted very well, but the lack of adequate solutions for rain water discharges led to water surface accumulation and the manifestation of the instability phenomena that have undetermined local trees. This is because trees with pivotal root have role of fixed deposit and disposal of water excess from the rock mass. We believe that the reforestation of areas affected by mining, is the most viable solution, although it may be alternated with other forms of recovery.

Fig.4; Pioneer plants on the surface of dump Bohorel. Examples of cochineal ( Phytolacca

decandra) in May 2009

45


References

1. Bell F.G., Bullock S.E.T., Halbich T.F.J., Lindsay P. (2001) Environmental impacts associated with an abandoned mine in the Witbank Coalfield, South Africa, International Journal of Coal Geology 45 2001 pag. 195–216 2. Coelho P., Silva S., Roma-Torres J., Costa C., Henriques A., Teixeira J., Gomes M., Mayan O., (2007) Health impact of living near an abandoned mine – Case study: Jales mines, Int. J. Hyg. Environ.-Health 210 (2007) 399–402 3. Domínguez-Cuesta María José, Jiménez-Sánchez Montserrat, Berrezueta Edgar (2007) Landslides in the Central Coalfield (Cantabrian Mountains, NW Spain): Geomorphological features, conditioning factors and methodological implications in susceptibility assessment, Geomorphology, 89, p. 358- 369. 4. Ghosem M. K., (2001) Management of topsoil for geoenvironmental reclamation of coal mining areas, Environmental geology (Environ. geol.), Springer, Berlin, ALLEMAGNE (1993) (Revue), vol. 40, nr. 11-12, pp. 1405-1410 5. Glade T., Anderson G. Malcom, Crozier J. Michael (2005), Landslide hazard and risk, Publiser Willey. 6. Hack R., Price D., Rengers N., (2002) A new approach to rock slope stability – a probability classification, Bulletin of Engineering Geology Environment, Springer-Verlag

7. Kitula A.G.N., (2006) The environmental and socio-economic impacts of miningon local livelihoods in Tanzania: A case study of Geita District, Journal of Cleaner Production 14 (2006), pag. 405-414 8. Klukanova Alena , Rapant Stanislav, (1999) Impact of mining activities upon the environment of the Slovak Republic: two case studies, Journal of Geochemical Exploration 66 (1999) 299–306 9. Merad M.M., Verdel T., Roy B., Kouniali S., (2004) Use of multi-criteria decision-aids for risk zoning and management of large area subjected to mining-induced hazards, Tunnelling and Underground Space Technology 19 (2004) 125–138 10. Segumpta Mritunjoy, (2003) Environmental impacts of mining: monitoring, restoration , and control, Lewis Publisher. 11. Walsby Jennifer Catherine (2007) Geohazard information to meet the needs of the British public and government policy, Quaternary International 171–172 (2007) 179–185 12. Zahiri H., Palamara D.R., Flentje P., Brassington C. M., Baafi E., (2006) A GIS-bassed Weight-of-Evidence model for mapping cliff instabilities associated with mine subsidence, Environmental Geology, Springer-Verlag 2006.

13. *** (1995) Environmental Risk Management, Best Practice Environmental Management in Mining, Edited by Environmental Protection Agency Australia.

46


POSSIBILITIES OF USE OF REMAINING GAPS IN THE OPEN PIT

Viorel VULPE*

Summary: This article examines the possibilities of use, the construction matters and the measures to ensure the stability of gaps remained after extraction of minerals by mining day works. Key words: remaining gap, waste rock deposit, deposit residue, storage reservoir, water filling, improvement measures, measures of consolidation and stability. Generalities

Mining industry contributes greatly to intensive pollution of environmental factors (water- air-soil), both in quantities of residues, and by their diversity.

A number of these economic units from the mining and quarrying industry, having the aim of extracting useful minerals by mining day works, in the near future will reach their limits of exploitation perimeters, and therefore exploitable reserve of minerals will run out.

Along with the depletion of this reserve of useful mineral, in the mining perimeter we find two distinct areas, to be rehabilitated: o first area, where during the process of extracting useful mineral has been stockpiled sterile, usually occupying areas which can reach up to hundreds of hectares (Rovinari coal basin open pits, Jilt, Motru, Berbeşti, etc.). o a second area, which lies between the waste dump and the open pit marginal slopes, called the remaining gap in specialized literature, a gap which can have more destinations, so that the work development will have found solutions to transform this "wound" caused by mining activity in a fully integrated structure in the region, with a highest possible utility.

The reasons supporting the need for remodeling and rehabilitation of land affected by anthropic activities from mining industry can include:

necessity of reintegration for degraded areas in the productive circuit reintegration and/or ecological of regions where they are, which leads to the regeneration of their economic potential;

improving environmental quality; eliminating the risk of slipping for

anthropogenic landforms occurred in the territory through sterile storage on dumps;

reducing slopes ensuring mitigation of erosion phenomena and accelerate process of the installation of vegetation; ____________________________________ *Eng.Ph.D stud. – SNLO Tg.Jiu, E.C. Roşia

removal of negative visual impact of the lunar-looking areas;

the possibility of creating new storage spaces for different types of waste and / or other materials in the remaining gaps on the open pits or on surface of waste dumps.

Depending on the purpose of rehabilitation of areas affected by mining operations we dignify the following types of interventions: initial configuration for landscape restoration; for change of destination use in accordance with

the requests of local community; for temporary systematization in waiting for

final decisions to be taken by the legal authorities. Estimating the volume and types of use remaining gap

It is well known that at any mining exploitation, after the depletion of geological reserve, there is a residual gap remaining because starting with the opening period and up to creating conditions for deposition sterile inside the open pit, in the operated area (internal dump) the material is deposited outside the mining field (external dump).

Exceptions make the open pits which close its perimeter in hilly areas and the open pit's bottom is on the same level or higher than the surrounding terrain. In this case, it can no longer be spoken of a remaining gap.

The volume of remaining gap in case of open pit can be appreciated by the equation:

Vg = Vh/ka + Vp where: Vg - is the volume of the remaining gap [m3] Vh - is the volume of steril e from outside dump [m3] ka - the loose coefficient of sterile deposited the outside dump [ %] Vp- total volume of extracted useful mineral [m3]

Under the legislation, any mining, either underground or surface, is required to give back in the economic cycle the affected areas after the opening works, preparation and exploitation of minerals.

In case of remaining gap, which is one of the resulted anthropic forms, along with other areas (outside dump, inside dump, surfaces occupied with social buildings, transportation, etc.) there are multiple opportunities for reuse.

If for the sterile deposits the rehabilitation works for restore purpose in the economic cycle can begin and are recommended to be performed in parallel with the extraction works, the use of remaining gap

47


involves a separate analysis in order to find optimal solutions for use. Among theseare mentioned:

the use of it as space for waste rock storage for new operating perimeters that open nearby;

use as ash deposit for thermo power plant; use as domestic waste deposit under preliminary

preparedness; water filling with different uses.

Depending on the operation methods, the sequence in time and space for works of opening,

preparation and exploitation, the ratio of overburden to coal, the resulted remaining gap can be: - remaining gap having the sides of slopes formed "in situ", as a lack of inside waste dump works, exemplifying through two natural lakes formed after the closure and withdrawal of equipment from Moi small open pit, the Rovinari coal basin, Gorj County. (figure 1) - remaining gap with both sides made of natural slopes and waste dump slopes, resulting from the waste roek storage in the exploited area.

Figure 1 Remaining gap of Moi small open pit, natural filled with water

Use of remaining gap as mine waste deposit This type of use requires an analysis which must

take into account the development perspective of extractive activities in the area, the feasibility of such project, the analysis of technical and economic opportunities in order to fix the transportation of sterile masses from adjacent perimeters and correlation of sterile volume, necessary to store, with the volume of remaining gap.

In case of using the storage space as a waste rock deposit for other operating perimeters, it is not necessary to apply other additional measures to ensure stability, in relation to the specific technologies for excavation, transport and storage.

In this view, it can be illustrated the case of Rovinari Est open pit, opened by an opening system imposed by the morphology of the area, through prosecution of excavation works into the Beterega mining perimeter, with advancement to the east, the waste rock being stored in the remaining gap from Beterega open pit.

The use of remaining gap as grounds deposit In order to use the remaining space from the

exploitation of useful mineral substance, as an ash deposit or as domestic waste dump, are required waterproofing measures to prevent the possibility of any radioactive waste or certain chemicals into the groundwater to the surrounding area, which can have serious environmental consequences for a very large extent.

Choosing the best waterproofing system is done considering a number of factors, such as: • the nature of waste to be stored; • hydrogeological conditions; • geomorphology of the region; • claims which may arise during operation; • the nature and characteristics of the used

material; The waterproofing must ensure:

• sealing of the entire deposit; • chemical and thermal stability towards stored

waste and rocks from foundation; • meeharieal strength for the efforts that occur

during construction and operation; • weather resistance (including frost, high

temperatures and ultraviolet rays); • dimensional stability to temperature variations; • aging resistance; • sufficient flexibility and tensile strength;

The achievement of ash deposits from the combustion of coal in power plants must take into account a number of technical economic and social criteria, among which are: Opportunity and need for planning ash deposit:

o in rating of deposits, calculation of storage capacity (area and volume of storage) must be taken into account the average amount of ash, given the period of operation for landfill of 15 to 20 years:

48


o deployment, building-up and dimensioning of the ash deposit to ensure optimal storage capacity with operating costs and minimum investment;

Constructive solution of the ash deposit: o considerations regarding the stability of the

ash deposit under negative effect of infiltrations;

o checking the ash foundation to overpressure;

Environmental protection measures and opportunities for reuse of the ash dump: o prevention of environmental pollution with

driven substances from deposits;

o prevention, in the neighboring areas, for occurred distresses by its structure damage and movement of these residues;

o protection of the air quality around deposit area;

o survey of the ash deposit behavior, through specific means, both during operation and after depletion of filling space ensuring environmental and economic reintegration of occupied lands;

Possibilities to use the thermo power plant ash as construction material.

Figure 2 Remaining gap of possibility to use the thermo power plant Rovinari

Use of remaining gap as basin

The easiest possibility to use remaining gap, resulted from the exploitation is the water reservoir, assuming different functions such as planning fishing, recreation area, storage tank for irrigation of agricultural land areas already played in the economic circuit, water supply in nearby settlements, water base organization.

In case of its use as water reservoir elaborate research are necessary to establish protection measures for submersibles slope stability and especially, when the gap is made up of areas with slopes "in situ", and landfill slopes., while the deposited material is heterogeneous and presents a loosening factor, being known the negative effect of water presence in slopes and flanks body, with implications for stability.

Note the importance of management in excavation activities, so that marginal slopes, which will delineate the accumulation of water, have a geometry that ensures stability conditions before reaching redevelopment of the remaining gap.

This consideration is important to avoid additional works related to slopes reshape or in the

unfortunate situation even to expropriation of neighboring lands for redevelopment of the marginal slopes.

Near the formed lake it is recommended the achievement of wooded areas, which contribute to the meeting of aesthetic requirements and the development of a vital area for the development of fauna in the area over the environmental benefits.

The appearance of reservoirs can cause some local changes, usually minor for climate that is difficult to differentiate between specific impact associated with the presence of water bodies and climate of the region with its normal fluctuations. The effects of water accumulation on the climate varies depending on the size of water accumulation (gloss surface water, lake depth), region topography and natural climate.

Tope climate speaking, the lake can print their own specific characteristics to weather elements and phenomena, creating a specific surface water top climate.

This can occur: lower temperatures; higher moisture;

49


downside of the air masses; the increased effect of wind due to flat; radiation and evaporation fog; stronger cloudiness; local precipitation; changes in evapo-transpiration;

Water mass can have effects of decreasing for local thermal variations, cooling air spring and summer and warming in autumn and early winter.

Possibility of water filling, use and constructive measures of water reservoir development

Considering filling with water of the remaining gaps is a long process it is recommended that measures of artificial filling and/or natural, with water, of these arrangements are made after ensuring stability and banks consolidation, taking into account the spatial dependence between the former open pit the marginal slopes of excavation benches and inside dump slopes.

The period of time necessary for residual gap filling is subject to possible quantities of water from natural sources of water supply and possible quantity from artificial sources, and the total volume of water required. As a water supply source maybe mentioned dewatering works.

The options of remaining gap filling, depending on the specifics of the area, can be:

natural: - using the potential of groundwater associated with dewatering works or water bearing formation opened inside open pit. The possibility of filling on a natural way is conditioned by the groundwater regime: flow, flow rate and piezometric level of intersected aquifers. - the precipitations which fall within the open pit perimeter and spill on the slopes, etc. If the dewatering works will not be executed, the maximum amount of water in the remaining gap will be stipulated by the following factors: infiltration flow from the marginal slopes; volume of precipitation; level of evaporation; possible share water effluent discharge for the

river area; morphology and dump's heigh beside the inner

surface of surrounding terrain; artificial:

- by directing water from the valleys located in the vicinity of the perimeter, with a minimum volume of hydro works for diversion and controlled their departure. - providing water supply from the river area by hydraulic works (channels adduct) or pumped supply system.

The possibility of artificial filling can be achieved through maintaining and running, after

depletion of excavation works, of possible free drainage drillings eruption and the use of the potential of water-bearing horizon with a minimum volume of hydraulic works, (the case of Roşia de Jin and Peşteana open pits.)

The artificial filling has some advantages: - the remaining gap function can take

considerably faster; - the operators can decide which is the

appropriate level of water in the lake; - there's a correlation between the arrangement

works (building and specific works according to final destinations ) and the amount of water directed into the future lake.

Planning and building solutions of submersed slopes

In most open pits, the resulted remaining gap is bordered on a side by the final slopes of the open pit, and on other side by the dump slopes, which consists of loose rocks.

In this case, on filling the remaining gap with water, the heterogeneous material which composed the entire waste dump undergoes rapid saturation (a first saturation), in their mass is forming a triphasic system (solid-liquid) that can initiate rock slides due to liquefaction.

To avoid the phenomena of instability, following solutions arc proposed to ensure the stability of dump benches slopes which will be submersed: • Waterproofing measures for dump benches slopes (figure 3 experience of mine operators in Germany -Grenfenhain open pit) Achievement of retaining walls or sand bags at

the foot of the submersed slopes; Use of geo grates for arrangement of the

submersed slopes (figure 4) The slopes covering with natural rocks filling

pieces of concrete that can be recovered from concrete platforms and access roads which will be decommissioned once the cessation of mining objective. (figure 5) Set out on the slopes surface hydrophilic plants.

It is also necessary to ensure protection of water storage area through the creation of forest belts width of 50 m consisted of hydrophilic plant species, water-loving (figure 6) Application of specific solutions to improve the

stability of (lump benches from vicinity of water filling by changing mechanical end physical features of rocks:

o surface consolidations; o depth consolidation - vibratory compaction; o consolidation through implantation of special inserts such geogrates or geosynthetics, etc;

50


Figure 3 - The experience of operators

Figure 4 The constructive principle and the way of development for dumps stability improving works using geosynthetics materials

Figure 5 Protective measures with rocks filling-the retention dam of Jiu river in Rovinari area

Figure 6 The protection of slopes through, set out of hydrophilic plants - Moi open pit

51


Use variants for water fillings For increasing the value of such facilities,

depending on the size of wafer fillings, there may be multiple uses such as: o stock pond; o water filling for irrigation or current water

supply;

o recreational area; o nautical base for performance sports, etc;

Depending on the type of water filings it will be required a specific development of the banks and bottom of the lake. General and specific constructive measures required to apply for such a type of reuse are presented in table 1.

Table no.l

Types of measures required to apply for different types of uses of water accumulation in the remaining gap Constructive measures

general specific Criteria number Type of use

Ensure dump slopes stability which will be submersed set up banks and lake base

1 fishy

#the banks will be planted with vegetation hydrophilic,

moisture-loving. #the base of the lake should be

as flat as possible

# dump slopes stabilization

immediately after the cessation of mining works, before filling

with water.

#compaction of slopes usingvibratory compaction

#partial substitution of the material by creating a

column filled with granular material.

2 irrigation #depth blasts for tamping

the material. #preload of the lands with or

without drainage.

#flattening of foreshores to avoid accidents (slides,

failures, etc.); #special measures to

ensure submersed slopes stability.

#vegetation should be chosen carefully. #use of the rock fill dams to

prevent erosion by wave of the banks.

#ensure the amount of water to fill the remaining gap.

#works of directed wetting or flooding of loess material

when compaction occurs under their own weight.

#works to improve the land stability so that it can run the parking areas, construction of

recreational and ancillary buildings. 3 recreation

#providing water level control in the remaining

gap through exhaust systems in the event of

force majeure.

#slopes waterproofing works with geotextile

materials.

# creating ways for ensuring connection with important

traffic routs in the area.

Conclusions

Possibilities to development and use of the remaining gaps resulted after the cessation of mining extraction works must take into account the following:

the perspective of mining activities development in the area;

area integration to be redeveloped into the neighboring natural environment;

analysis of alternative uses of certain goals that they lose utility at the same time with the cessation of mining activities;

the land morphology resulted from the technological activities in the open pit; Starting with the possibilities of remaining gaps usage, from the open pits which run out

52


their activities, it is taken into account the following:

In case of remaining gap use as waste rocks deposit - for other operating perimeters, no further measures are necessary to ensure slopes stability beside any specific measures in case of excavation, transport and stockpile technologies for operating open pits.

For remaining gap use as residues deposit - ash deposit or domestic depositor, special measures are needed for construction and specific measures for rehabilitation and restoration in the economic cycle;

Development of remaining gap as storage lake - gives the possibility of using water in all its forms being rated as an economic good.

Therefore: - By the development of the remaining gap as

storage lake, the water is used efficiently and equitably with an important role in the conservation of the water resources of the area.

- The integrated management of water combines the matters involving the use of water with the once of protection for natural ecosystems.

- It is ensured restoration of groundwater level (hydrostatic level) much faster than in any other way of gap usage.

References 1. Fodor, D., Băican, G. The impact of mining industry against environment – Editura Infomin Deva 2001; 2. Lazăr, M. The surface water management - Editura Universitas, 2001; 3. Lazăr, M. Ecological rehabilitation - Editura Universitas, 2001 4. Rotunjanu, I. The stability of versants and slopes -Editura Infomin 2005 5. *** Technical standard regarding the risk assessment of landslides occurrence in the road area 6. *** Technical standard regarding waste storage, establishment, operation, monitoring and closure of waste deposits.

53


POSITIONAL SYNTHESIS OF THE SLIDER-CRANK INVERTED MECHANISM

Vasile ZAMFIR*, Horia VÎRGOLICI**, Olimpiu STOICUŢA***

Abstract In the paper we present the positional synthesis of the slider-crank inverted mechanism as part of mining machines and equipment.

Introduction

In figure 1 is shown the slider crank inverted mechanism. The dimension e represents the eccentricity of the crank guideway. The contour vectorial equation, in relative dimensions, can be written with the notations in the figure by referring to the AD dimensions.

Fig. 1 The slider crank inverted mechanism and the

geometrical parameters that define it (a,e,φ0,ψ0) aeBC ++= 1 (1)

By squaring and taking into account that: )cos(21)( 0

2222 ϕϕ +−+==+ aateBC (2) we obtain:

0)cos()cos( 000 =++−−+− ψψϕϕψψae (3)

From equation (3) it results that the rotating output element is dependent on four geometric parameters: a, e, φ0 and ψ0. The calculus of three parameters

Let us suppose that we want to determine the parameters a, e and φ0 (the ψ0 parameter being chosen arbitrarily). In this case the equation (3) is expanded under the form:

0)cos(sin)sin(cos)cos(

000

00

=++−+−−−+−

ψψϕϕψψϕϕψψ

aae

(4)

____________________________________ * Prof.eng. Ph.D – University of Petroşani **Lect. Ph.D - Univ. „Spiru Haret” Bucureşti *** Asist.eng. Ph.D – University of Petroşani

and then it is identified with the following interpolation polynomial:

0)()()( 221100 =+++ ϕϕϕ fpfpfp (5) where:

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

=

=

=

02

01

00

cos1

cos

ϕϕ

ϕ

tgpa

p

aep

(6)

⎪⎩

⎪⎨

⎧

−+−=+=

−+−=

)sin()cos(

)cos(

02

01

00

ϕψψψψ

ϕψψ

fff

(7)

In order to determine the three coefficients p0, p1 and p2, the values of the functions f0(φ), f1(φ) and f2(φ) will be calculated for a set of values of angle φ (φ1, φ2 and φ3) in the approximation interval (φ0,φm) chosen arbitrarily or by Chebyshev spacing. A system of three linear equation in pj, j=0,1,2 is obtained:

⎪⎩

⎪⎨

⎧

=+++=+++=+++

0)()()(0)()()(0)()()(

322311300

222211200

122111100

ϕϕϕϕϕϕϕϕϕ

fpfpfpfpfpfpfpfpfp

(8)

After finding the parameters p0, p1 and p2 with formulae (6), the mechanism unknown parameters are determined, in the following sequence:

0001

20 cos;cos

);( ϕϕ

ϕ apep

eaparctg === (9)

Error analysis The real value of angle ψ = ψr can be calculated

with one of the following relations:

te

a

arctgr arccos1)cos(

)sin(

0

00 ±

−+

+=+

ϕϕ

ϕϕψψ (10)

where

)cos(21 02 ϕϕ +−+= aat (11)

or with the relation deducted from the position equation (3), written under the form of equation (12) in sin(ψ0+ψ) and cos(ψ0+ψ):

0)cos()sin( 00 =++++ CBA ψψψψ (12)

54


whereby it results

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−−+±

=+ii

iiiii CB

CBAAarctg

222

0 2ψψ (13)

where

⎪⎩

⎪⎨

⎧

=++−=

+=

eCaB

aA

i

ii

ii

1)cos()sin(

0

0

ϕϕϕϕ

(14)

The position deviation of the Δψ(φ) crank guideway is compared to the allowable value for several values φi in the approximation interval (φ0, φm):

adr ψψψϕψ Δ≤−=Δ )( (15)

The calculation of four parameters

The position equation (3) is written under the form of the following polynomial in order to calculate all the four parameters:

0)()()()( 33221100 =+++++ ϕϕϕϕ fpfpfpfp (16) where:

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

=+=−=

=

01

0002

0001

00

)coscos()sincos(

cos

ψϕϕψϕϕψ

ϕ

tgptgaptgap

ap

(17)

⎪⎪⎩

⎪⎪⎨

⎧

−=−−=−−=

=

ψϕψϕψ

ψ

sin)cos(

)sin(cos

3

21

1

0

ffff

(18)

The abscissas of the interpolation nodes within the approximation interval (φ0,φm) are chosen arbitrarily or with the Chebyshev spacing. The system of four linear equations in pj, j=0,1,2,3 is written and solved.

The unknown parameters of the mechanism are determined in the following sequence:

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

+=

=−

==

000

2

2

100

00

30

cossin

)(

cos

ϕϕψ

ψϕ

ψψ

tgpa

pptg

peptg

(19)

Supplementary conditions

Conditions regarding the elements length

In the case of the mechanism with rotating slotted link, the following relations have to be fulfilled regarding the elements length:

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

≥≤

≤≥

≥≤

LeaLe

eLaL

aL

eLa

;

;1

1;

(20)

The transmission angle In the case when element AB is the driving one,

the transmission angle is the angle γ, made between the directions of the absolute velocity of point B (perpendicular on t) and the direction of the relative velocity (parallel to the sliding direction of the slipper).

Rotating the sides of this angle clockwise, we obtain the angle made between a perpendicular direction on the sliding direction BC and the direction BD..

From Fig it results:

te

=γcos (21)

Taking into account relation (11), we get:

)cos(21cos

02 ϕϕ

γ+−+

=aae

(22)

From relation (22) we deduce that γ = γmin for φ+φ0 = 0:

1cos min −

=a

eγ (23)

Therefore, the condition of the transmission angle can be given by relation:

ea ad ≥− γcos1 (24)

From figure 1 it results that slotted link rotates if:

ea +> 1 (25)

From the inequalities (24) and (25) it can be inferred that for a > 1 and by fulfilling the condition (15) the mechanism with rotating slotted link is obtained. In this case, of the inequalities (20) only the following must be fulfilled:

⎪⎪⎩

⎪⎪⎨

⎧

≥

≤≤

Le

eLaLa

1 (26)

If ea +< 1 (27)

by rotating the crank AB, the slotted link will have an oscillating motion.

In order to satisfy condition (24) it is necessary to comply with the following inequality:

55


ad

eaγcos

1−≤ (28)

which comprises also relation (20). From the inequalities (20) the following must

be fulfilled:

⎪⎩

⎪⎨

⎧

≥≥

≤≥

Lea

Le

eLaL

a

;1

;1

(29)

The synthesis of the crank guideway mechanism

In figure 2is shown the two crank guideways mechanism and its geometrical parameters.

Fig. 2 Two crank guideways mechanism and its

geometrical parameters

This mechanism contains two crank guideways: a rotating one having the AB direction and a sliding one having the CD direction. This mechanism is called tangential mechanism.

The mechanism has three geometrical parameters: e, h and φ0.

Using the notations in figure 2, we can write: 0)( 0 =+−+ ϕϕtgesh (30)

In order to determine the three parameters, the equation (30) can be written under the following polynomial:

0)()()( 221100 =+++ ϕϕϕ fpfpfp (31)

where

⎪⎩

⎪⎨

⎧

=+=

−=

02

01

00

ϕϕ

ϕ

tgptghep

hetgp (32)

⎪⎩

⎪⎨

⎧

==−=

ϕϕtgsf

tgfsf

2

1

0

(33)

For a set of three values of angle φ (φ1,φ2,φ3) in the approximation interval (φ0,φm), considered as abscissas of interpolation nodes, arbitrarily chosen or by Chebyshev spacing, we can write three linear

equations, from which we determine the coefficients pj, j=0,1,2 using the relations (32). We determine the geometrical parameters, first

20 arctgp=ϕ , then e and h from the following system:

⎩⎨⎧

=+=−

10

00

ptghephtge

ϕϕ

(34)

Error analysis The relation (30) expresses the deviation

between what the guideway can do and what has been imposed to. This deviation must verify the following relation, where Δsad represents the permissible deviation:

adshstges Δ≤−−+=Δ )()( 0 ϕϕϕ (35)

Supplementary conditions The transmission angle γ results directly from

figure 2:

eshctg +

=γ (36)

In order to satisfy the condition of the minimum transmission angle, the following relation must be fulfilled:

adctgesh γ≤+ max (37) where smax is the maximum displacement of the driven element, γad is the permissible transmission angle, h is the distance between the reference axis and the initial position of slide B.

Earlier in the paper, the driving element is the rotating slotted link. In this case, the mechanism generates the function f(φ; e, φ0, h). When the sliding slotted link is the driving element, the mechanism can generate the identical function f(s; e, φ0, h). As a conclusion, the two crank guideways mechanism doesn’t depend on the driving guideway. Numerical examples

Let synthesize a slider-crank inverted linkage for four simple accuracy points to approximate the function

( ) 2 / 25ψ ϕ = ϕ (38)

on the interval 0 0ϕ = , 50=mϕ . Solution. The interpolation nodes are chosen

by Chebyshev spacing: 0

1

02

03

04

1 cos 1,9030122 8

31 cos 15, 4329142 8

31 cos 34,5670862 8

1 cos 48,0969882 8

m

m

m

m

ϕ πϕ

ϕ πϕ

ϕ πϕ

ϕ πϕ

⎧ ⎛ ⎞= − =⎜ ⎟⎪ ⎝ ⎠⎪⎪ ⎛ ⎞= − =⎪ ⎜ ⎟⎪ ⎝ ⎠⎨

⎛ ⎞⎪ = + =⎜ ⎟⎪ ⎝ ⎠⎪

⎛ ⎞⎪ = + =⎜ ⎟⎪ ⎝ ⎠⎩

(39)

56


The system (16) (with the explanatory relations (17) and (18)) of four unknowns pj, j=0,1,2,3 is solved, obtaining the solutions:

0

1

2

3

0.743680.44078

1.731550.22851

pppp

=⎧⎪ =⎪⎨ = −⎪⎪ = −⎩

(40)

The unknown geometrical parameters of the synthesized linkage are calculated in relations (19):

00

00

12.872080.72499

27.154081.74187

e

a

ψ

ϕ

⎧ = −⎪

=⎪⎨

= −⎪⎪ = −⎩

(41)

We calculate ψr with relations (10)-(13) and with relation (15) we calculated the deviation Δψ(φ), which is compared to the allowable value for several values on the approximation interval (φ0,φm), relation (15).

In order to render evident the way angle ψr (13) varies in relation to ϕ we shall present this function graphically together with the function ( ) 2 / 25ψ ϕ = ϕ . In figure 3 the angle ψr is shown

with the red colour and the angle ( ) 2 / 25ψ ϕ = ϕ in the interval (φ0,φm) is shown with the blue colour.

Fig. 3 The variation of the angles ψr and ψ in

relation to φ

The way deviation Δψ(φ) varies in relation to φ is shown graphically in the figure 4:

Fig. 4 The deviation Δψ(φ) in relation to φ

References 1. Zamfir V., Vîrgolici H. Condiţii de sinteză prin metoda interpolării Revista Minelor, vol 17, nr. 1 / 2011

2. Lazăr M., Pandrea N., Popa D. Obtaining Cebâşev-type mechanisms through optimal synthesis based upon some caalculus programs Mec. Apl., Bulletin of the University of Piteşti, 2001

3. Georgescu T., Lazăr M. Cebâşev-type mechanisms obtained through the optimum synthesis based on some calculus programs Scientific Bulletin automotiveAutomotive, no. 19, vol 1., University of Piteşti, 2002

4. Artobolevski I.I., Levitski N.I., Cercudinov S.A. Sintez ploskia mehanizmov Fizmatigiz, Moskva, 1959 5. Beleţki V. Rasciot mehanizmov maşin avtomatov piscevâh proizvodstv, „Vişa scola”, Kiev, 1974

6. Cercudinov S.A. Sintez ploskih şarnirnorîciajnîh mehanizmov Iz-vo Academii Nauk S.S.S.R., Moskva, 1959

7. Dancea I. Programarea calculatoarelor numerice pentru rezolvarea problemelor cu caracter tehnic şi de cercetare ştiinţifică Ed. Dacia, Cluj-Napoca, 1973

8. Hartenberg R.S., Denavit I. Kinematic Synthesis of Limkage McGraw-Hill Series in Mechanical Engineering, New York.

9. Lazaride Gh., Stere N., Niţă C. Mecanisme şi organe de maşini Ed. Didactică şi Pedagogică, Bucureşti, 1970.

10. Sarkisean Iu.L, Cecean G.S. Optimalnîi sintez peredatocinovo cetîrzvenika Maşino-beledenie, nr.3, 1969.

11. Tesar D. The Generalized Concept of Three Multiply Separated Positions in Coplanara Motion Journal of Meechanisms, vol.2, 1967, p.461-474

12. Tesar D. The Generalized Concept of Four Multiply Separated Positions in Coplanara Motion Journal of Meechanisms, vol.3, 1968, p.11-23

13. Zamfir V. Sinteza mecanismelor cu bare articulate plane (Note de curs), fasciculele 1-5 Litografia Institutului de Mine, Petroşani, 1976, 1977.

57


PERSONALITIES AMONG US “A dream come true”- Prof. Ph. D. eng. D.H.C. Ştefan Covaci

at the age of 90 years old

On October 07, 2011, inside the Department of Mining Engineering, Surveying and Construction from the University of Petroşani it took place the festivity for celebrating the Prof. Ph. D. eng. D.H.C.Ştefan Covaci at the age of 90 years old.

*** Professor Ştefan Covaci was born in Petrila, a

mining town situated on the bank of Eastern Jiu River, on October 9, 1921, in a miners family. He attended the courses of the first four forms at the Primary School in Petrila, and the next four of high school forms in Petroşani. Because of the financial difficulties at the age of 14 years he had been employed as a day laborer in the Petrila mine for 2 years, and then he was switched to underground. Eager to continue his studied, he enrolled at the School of Mining Foremen in Petroşani that in 1945 became the School of Sub-Engineers, which he graduated in 1947. In the same year he enrolled at the Polytechnic Institute in Timişoara, Mining Faculty that he completed with the mark ”cum laude” having been assigned at the Mine in Derna-Tătăruş.

During 1949-1953 he continued his studies at the Mining Institute in Saint Petersburg. After this period he worked as a temporary university professor at the Mining Institute in Bucharest. In 1956 he was appointed as a director of Institute of Coal in Petroşani and in 1957, when it was focused on the higher education in Petroşani, he was appointed as rector. His teaching activity was developed as a university professor until 1990 when he was retired. He held the positions of rector and head of department. Since 1990 he had worked as a teacher consultant until 2004 and he still maintains a close connection with the mining school in Petroşani.

Since 1967, he received a doctoral right under his direct guidance and obtained the Ph.D. title, 19 specialists in the mining field.

Through his scientific experience or his teaching talent during he worked in the mining of higher education, his attention was directed toward: developing the mining science and technology, training the curricula and teaching; widening contacts between the higher mining schools in Petroşani with other prestigious universities abroad.

Together with Professor Covaci, many teachers worked into the underground mines, some of whom there are renowned experts in production today, but also those who now form the basis of the mining school in Petroşani. Professor Ştefan Covaci is the

one who wrote the first manual and treaty in the field of underground mining, works that the students learn after and the Ph. D. students study after, but also refresh their knowledge and those working in production, research and design.

Professor Covaci is a man of high reputation stint with recognition and appreciation in the development of mining science, both domestically and worldwide. The activity produced a large number of works of great value, which he published in journals and scientific papers in the country and abroad and has supported international conferences and congresses. Thanks to his prestigious activities in 1960 he was elected a member of the Romanian Mining Committee and became an active member of the International Organizing Committee of World Mining Congress Mining. From 1960-1989 he worked steadily in the International Organizing Committee, the messenger stint Romanian mining, making the high school achievements to be known worldwide the mining school of Petroşani.

In 1989 prof. Ph.D. eng. D.H.C. Ştefan Covaci was named Honorary Member of the International Committee for his contributions to the development of the mining science around the world.

*** At this ceremony there were attended many

teachers from the university, as follows: the Rector, Prof. Ph.D. eng mat. Emil Pop, the former rectors -.

Prof.Ph.D.eng. Dumitru Fodor, Prof.Ph.D. eng. Nicolae Dima, some specialists of high reputation, who led to their shoulders the manufacturing activity in the Jiu Valley: Eng. Iulian Costescu (former General Manager and Deputy Minister), engineer Victor Apostu (former assistant of the professor Ştefan Covaci and former Manager of mine), Ph.D. eng Voicescu Benor (former Manager of mine), Eng. Tomuş Alexander (former Ph. D student of Prof. Ştefan Covaci and Head of current laboratory of ICPMC Petroşani), ec. Bârsan Iosif (former economic manager, a close friend of Professor Ştefan Covaci) and journalists from local newspapers.

The Festive meeting was opened by the Director of the Department of Mining Engineering, Surveying and Construction, Prof. Ph. D. eng Constantin Semen, which showed that all Prof. Ştefan Covaci work of training took place in this department (formerly named the Mining Department) which continued to strengthen the prestige obtained at the time when Professor Ştefan

58


Covaci was a rector of the Mining Institute and head of this department.

The Dean of the Mining Faculty, Professor Ph.D. eng. Ioan Dumitrescu, in his speech said that "… today is the event on our gratitude to all Your work, ...You have managed to awaken the conscience of many of us, the real value ... and you had no strategy for the people to love you. Our duty is to keep alive the history of this institution, written by personalities like you ". During this ceremony, the Dean of the Mining Faculty handed to Professor Ştefan Covaci the "Diploma of Excellence" as a tribute to his whole career.

Rector of University of Petroşani - prof. Ph.D. eng. mat. Emil Pop - noted the mark of Prof. Ştefan Covaci personality to this institution since its establishment until today. "The difficulties that they faced the University of Petroşani, the teachers were able to go through all the vicissitudes of life, throughout its history. The greatest wealth of this school is the teachers who managed to overcome all these difficulties "- said the rector Emil Pop. During this festivity, the rector handed, from the office of the Senate, to the first rector of the Mining Institute of Petroşani, during 1956-1963, the "Diploma of Honor". Taking the word to the conclusion of the ceremony of Rector said to Professor Ştefan Covaci that "... it is our spiritual father and supporter of all our schools. School is based on some pillars, and Professor Ştefan Covaci is the main pillar. "

Prof. Ph. D. Badulescu Dumitru, the former assistant to the professor Ştefan Covaci, was invited to read the message of the Department of Mining Engineering, Surveying and Construction, as an expression of gratitude of the teachers from this department and in particular from the teaching staff from mining department to the contribution of the great personality of Prof. Ştefan Covaci to the development of this department "You have made generations of graduates who have awakened a sense of dignity, professional dedication and love for their chosen profession. In all mining areas in the country and even abroad, the former students will appreciate your and remember with pride that you were a teacher "- quote from this post.

Under the motto "God love teacher," he based his entire speech of the Eng. Benor Voicescu. This is a romantic journey across the biography of Professor Covaci, remembering the events, characters and figures, gleaned from autobiographical work "A dream come true" written by professor at the age of 81 years. "There are people who put their final stamp to their personality on those who come in contact and whose success is confused with the glory of the nation watches and intellectual prestige of a nation" - said at the end of

his intervention Voicescu engineer, referring to "with love "the personality of Professor Ştefan Covaci.

Ph. D. Eng. Alexandru Tomuş , in his speech, expressed his gratitude to the professor Ştefan Covaci, who was a professor and doctoral supervisor and compare it "a self-diamond" grinding over 9 decades with much talent and hard work.

The former rector of the Mining Institute of Petroşani, during1979 -1989, Prof. Ph. D. eng. Dumitru Fodor, in his speech, said about Prof. Ştefan Covaci: "It is a life that I lived with Professor Ştefan Covaci. The first impression about the Rector and Professor Ştefan Covaci was very strong. I was pleased and honoured to work with him. I had admired for his reliability, his hard work and his results. He was a master. He inspired and coordinated so many activities of team. Prof. Covaci wrote the first scientific literature of mining in Romania, signing first treated by mines. A supported effective work in international organizations, where he made known what it is happening in higher education and in Romania Mining activity inside the International Organizing Committee, whose membership is over 50 years, he has been successful since1972, when he organized the VI-th World Mining Congress in Romania, which was attended by over 2,000 professionals from over 50 countries. I am proud that I grew up and worked with Professor Ştefan Covaci ".

Prof. Ph. D: Viorel Voin - prorector, expressed his admiration for the life and personality of Professor Ştefan Covaci. To exit the prosaic speech, just reread a poem dedicated with much love, "the first rector Ştefan Covaci," by engineer Cornel Burlec, at 50 years after graduating in 1960 and adapted promotion celebrating the new context of the teacher.

Head of Management, Environmental Engineering and Geology Department, Prof. Ph. D. eng. Maria Lazar, paying a homage to Professor Ştefan Covaci she noted that ".. the name of Professor Stefan Covaci is an emblem of what the Institute of Mining was and the University of Petroşani was, ...and former students remembered with love by Professor Ştefan Covaci ".

Prof. Ph. D. Ilie Rotunjanu, the former dean of the Mining Faculty during the period 1984-1990, among the others, in his speech said: "I make myself the messenger of this generation and I want to assure you of all the admiration of this generation that you appreciate and admire you .... You made the first treaties of mines. I am proud that you made us to be known in the country and abroad, who have fought the prestige and reputation of our school abroad". On this occasion, Professor

59


Rotunjanu asked professor Ştefan Covaci to write a message on the first treaty by mines, which will be donated to the University of Petroşani for the whole historical memory of this institution.

We selected from the intervention of prof. Ph. D. Eng. Nicolae Dima, the former rector of the University of Petroşani, during 2004-2008, the following: "As a student as I moved during the second year from Bucharest. The school was intended to represent the higher education at the country level. This was done under the distinguished leadership of Professor Ştefan Covaci. As a student, I had due regard to the rector of this institution. He was a great trainer of people, professional and educational aspect. Professor Ştefan Covaci behaviour had a profound impact on my generation especially, and other generations. "

At the end of these interventions, marked by a profound motion, spoke birthday, the distinguished professor Stefan Covaci. He thanked everyone for their kind words expressed on this festive occasion, wishing them health, happiness and fulfilment of at least "90 springs". "For me, today is a special day because of your love and joy for meeting you again and many memories that bind us. On this occasion I am reminded of my teachers, my colleagues, my generation and my students. The figures of my teachers were printed in my heart. Thanks to them I made a series of objectives. This means that my life has not passed in vain”.

Prof. Ph.D. Eugen Cozma, mining eng., Prof. Ph.D. eng Ilie Onica, mining eng.

(former assistants of Prof. Ştefan Covaci)

Prof. Ph.D. eng. D.H.C.Ştefan Covaci Four rectors of University of Petrosani – from the left to the right:

Prof. Ph. D. eng. Nicolae Dima, Prof. Ph. D. eng. mat. Emil Pop, Prof. Ph. D. eng. Ştefan Covaci, Prof. Ph. D. eng. Dumitru Fodor

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Documents

nr. 4 EN/2011