J. Cent. South Univ. (2021) 28: 100−111 DOI: https://doi.org/10.1007/s11771-021-4589-x

Contour blasting parameters by using a tunnel blast design mode

Nguyen Ngoc MINH1, 2, CAO Ping(曹平)1, LIU Zhi-zhen(刘智振)1

1. School of Resources and Safety Engineering, Central South University, Changsha 410083, China; 2. Quang Ninh University of Industry, Quang Ninh 208650, Vietnam

© Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2021

Abstract: The quality of contour blasting depends on many initial blasting parameters. The parameters including blasthole diameter, rock Protodyakonov coefficient, tunnel area and distance between cracks on the tunnel face are more important. In this study, an algorithm linking between Delphi programming language and AutoCAD was created to develop a tunnel blasting model. Using this model, tunnel contour blasting passport in AutoCAD can be obtained automatically. The effects of rock Protodyakonov coefficient and cracks’ distance on blastholes number and specific charge with the variation of blasthole diameter and the semi-circular tunnel face area were investigated to yield a set of equations with the highest correlations. The results show that specific charge increases as rock Protodyakonov coefficient, cracks’ distance and drillhole diameter increase, but decreases when tunnel face area increases. In addition, the number of drillholes increases linearly as tunnel face area increases but decreases when drillhole diameter increases. Key words: contour blasting; blasting model; blasting passport; tunnel blasting Cite this article as: Nguyen Ngoc MINH, CAO Ping, LIU Zhi-zhen. Contour blasting parameters by using a tunnel blast design mode [J]. Journal of Central South University, 2021, 28(1): 100−111. DOI: https://doi.org/10.1007/s11771-021-4589-x.

1 Introduction

There are two main rock excavation methods, blasting and machining. The blasting method is preferred to use since its low initial investment and easy to deal with different shapes and sizes of openings [1−3]. The contour blasting method has been widely used for long-term underground construction such as the construction of mountain tunnels, principal mining excavations, and hydroelectric projects with the main purpose of minimizing overbreak or underbreak volume and creating a well-shaped boundary [4−6]. In a designing contour blasting passport process, the principal blasting condition parameters, including rock properties, rock fragmentation, blasthole diameter, explosive type and tunnel area should be

determined as the primary parameters. The most important part of blasting passport designing is to give an initial estimation of the relation between principal blasting condition parameters and blasting result parameters. SOROUSH et al [7] investigated the relations between tunnel face area and blasthole diameter with the blasting result parameters for rectangular tunnel section shape using parallel cuts and angular cuts methods. In this research, an algorithm linking between Delphi programming language and AutoCAD was created to develop a tunnel blasting model, namely VOLVN. Using the VOLVN model, the tunnel contour blasting passport in AutoCAD can be obtained automatically. The model can be used for investigating the effect of blasting conditions on blasting results for semi-circular tunnel face area using parallel hole cuts method. In this regard, the relations between

Received date: 2020-03-23; Accepted date: 2020-06-12 Corresponding author: CAO Ping, PhD, Professor; Tel: +86-13973128263; E-mail: pcao_csu@sina.com; ORCID: https://orcid.org/

0000-0003-3192-0267

J. Cent. South Univ. (2021) 28: 100−111

101

rock Protodyakonov coefficient, cracks’ distance and total blastholes number, specific charge with the variation of blasthole diameter and the tunnel area were investigated to yield a set of equations with the highest correlations. This paper firstly outlines how the VOLVN model was developed, and then introduce the model interface and working procedure. Afterward, contour blasting design parameters in different conditions are calculated and achieved results are ultimately analyzed. 2 VOLVN model development method 2.1 Proposal for parallel hole cut methods In order to design a tunnel blasting model, the tunnel face should be divided into different sections. The energy balance model proposed on dividing tunnel face into three sections: cut section, production section and profiling section [8]. HOLMBERG [9], OLOFSSON [10] and ZHOU et al [11] proposed dividing tunnel face into five sections as seen in Figure 1. The VOLVN model was an empirical model designed by dividing the tunnel face into cut, stoping, contour and lifters sections. Based on the combination of three standard parallel hole cut methods proposed by NTNU model shown in Figure 2 [12] and practical

Figure 1 Tunnel sections [9−11]

Figure 2 Three standard parallel hole cut methods

proposed by NTNU [12]

research, the VOLVN model provides four parallel hole cut methods, as shown in Figure 3. The distance between parallel drillholes is automatically calculated depending on the amount and diameter of empty drillhole as JIMERO et al [13] proposed. The cut method is selected depending on the drilling machine type, the face advance for one cycle and the tunnel area. The first cutting method is used for small tunnel section, manual drilling machine and the face advance for one cycle less than 2.8 m. The second cutting method is used for small to medium tunnel section, one arm types of jumbo drilling machine and the face advance less than 4.0 m. The third and fourth cutting method is used for large section, double-arm types of jumbo drilling machine and face advance up to 6.0 m.

2.2 Proposal for calculation of contour hole parameters

In each operation of designing smooth blasting passport, the determination of burden and charge concentration for contour blastholes is extremely important since it affects the smoothness of the tunnel boundary. OLOFSSON [10] proposed burden and charge concentration depending on explosive type and drillhole diameter, ZHANG [14] pointed out that the burden value may depend on

Figure 3 Parallel hole cut methods proposed by VOLVN model

J. Cent. South Univ. (2021) 28: 100−111

102

many factors such as diameter of drillhole, decoupled charge, rock properties, explosive type, specific charge, wave attenuation, fragmentation, production and productivity [14]. From existence blast design models, the burden can be determined by the interaction of many factors. The burden value in the NTNU model depends on rock blastability, drillhole diameter hole length and tunnel cross-section. In the Swedish model, the burden depends on drillhole diameter, fixation factor, rock constant, explosive type and spacing/burden ratio [12]. The burden value in VOLVN model depends on: 1) Diameter of drillhole Rock Protodyakonov coefficient, which is presented for rock properties and widely applied in China [15] and Vietnam [16], is determined from the uniaxial compressive strength of the rock as [17]: f=σP/K (1) where f is the Protodyakonov coefficient of the rock; σP is the rock’s uniaxial compressive strength in MPa; K is a constant equal to 10 MPa. The standard classification indexes for rock mass blastability in relation to rock Protodyakonov coefficient are resumed by LU [18] in Table 1. Table 1 Classification standards of rock mass blastability

[18] Blastability

class σt/MPa f

Characterization of blastability

I ≤1.5 ≤2.5 Very easy

II 1.5−3 2.5−6 Easy

III 3−6 6−10 Moderate

IV 6−12 10−18 Difficult

V ≥12 ≥18 Very difficult

Note: σt is rock tensile strength.

3) Explosive type 4) Distance between cracks on tunnel face, which is presented for the fragmentation of rock and determined by measuring directly in situ. 5) Face advance of one tunneling cycle Both values of burden and charge concentration can be determined by empirical method. LANGEFORS et al [19] proposed the results table from investigations and practices in Europe and the USA are shown in Table 2. By using the graphic analysis method, it is

Table 2 LANGEFORS proposal of relation between

burden, charge concentration and drillhole diameter Drillhole

diameter/mm Burden/m

Charge concentration/(kgꞏm−1)

30 0.7

37 0.9 0.12

44 0.9 0.17

50 1.1 0.25

62 1.3 0.35

75 1.6 0.5

87 1.9 0.7

recognized that the relation among burden, charge concentration and drillhole diameter is mostly linear as shown in Figure 4.

Figure 4 Relation between drillhole diameter with

burden and charge concentration

According to NOGEL [20] who did a study using drillhole diameter of 36 mm and Ammonite No. 6 explosive substance, it is proposed that the burden (B, m) and charge concentration (q, kg/m) can be determined by distance between cracks on the tunnel face (dc, m) and Protodyakonov coefficient of the rock (f ) with following formulas [20]: The burden: B=0.9−0.25Kc (2) where Kc is the relative cohesion coefficient, Kc=1 when dc>1, Kc=0.1+(dc−0.2) when 0.2≤dc≤1, and Kc=0 when dc<0.2. The concentration of the charge: Q=[0.4+Kc(0.58−0.032(67/f−1.7))]B (3) The VOLVN was modeled relied upon the proposal of NOGEL [20] and LANGEFORS et al [19] to generate the following formulas: B'=0.9−0.25Kc+0.0205(d−36) (4)

J. Cent. South Univ. (2021) 28: 100−111

103

q'={[0.4+Kc(0.58−0.032(67/f−1.7))]B+ 0.0115(d−36)}(360/A) (5) where 0.0205 is drillhole diameter correlation of burden achieved by function in Figure 4; d is drillhole diameter; 36 mm is drillhole diameter using NOGEL [20] research proposal; 0.0115 is drillhole diameter correlation of charge concentration achieved by function in Figure 4; 360 cm3 is lead bomb expansion achieved by using Ammonite No.6 explosive substance; A is explosive detonating pressure achieved by doing lead bomb expansion experiment (cm3). 2.3 Proposal for algorithm linking between

Delphi programming language and AutoCAD

One of the main purposes of developing VOLVN model is creating a blasting model that can link calculation blasting result parameters and process of drawing blasting passport in AutoCAD. Using the model, the tunnel contour blasting passport in AutoCAD can be obtained automatically. There are several methods to draw automatically in AutoCAD, such as: 1) Using Script file. 2) Using DFX text files. 3) Using Lisp, Object ARX, and VBA programming languages. Among those methods, using Script file method is simple because it is close to the manual drawing labor. These following steps are working procedure of the model: 1) Relying on specialized knowledge to calculate parameters of blastholes and blasting pattern. 2) Taking the AutoCAD origin coordinates (0, 0) as a base point to calculate coordinates of blastholes. 3) Combining the calculated coordinates of blastholes and the AutoCAD drawing commands to create a script file that allows drawing automatically blasting passport. For example, drawing a semi-circular tunnel with a height of h and a width of B, VOLVN model must create a Script file with the following contents: pline 0, h@0, −h@B, 0@0, h arc SB/2, (h+B/2) 0, h

(6) Hence, the interactive features and algorithms

linking between Delphi programming language and Auto CAD were examined and developed. VOLVN model was designed to exporting a Script file that can be used to draw blasting passport in AutoCAD automatically. 2.4 Interface and working procedure of VOLVN

model VOLVN model was programmed by Delphi programming language, consisting of 8000 code lines and capability of running directly in all versions of Windows without installation. The working procedure of VOLVN model is presented by the following example which is one of the blasting passports created during the construction of DakMy3 hydropower project. The blasting conditions are as the following: 1) Tunnel section shape: semi-circular with 6.5 and 6.2 m in height and width, respectively. 2) Number of empty holes for parallel methods: one 102 mm diameter hole per each cut and 38 mm diameter for charged holes. 3) Explosive type: Ammonite AD1 with following characters: lead bomb expansion (detonating pressure) of 350÷360 cm3, explosive speed 3.600÷4.200 m/s, specific gravity of 950÷1050 kg/m3. 4) The rock Protodyakonov coefficient f=7. 5) The distance between the cracks on the face is 0.7 m. 6) The face advance of one tunneling cycle is 3 m. In the first windows, the introducing initial data are shown in Figure 5. The model will automatically calculate and update blasthole parameters. The results are shown in Table 3 and the economic-technical indices are shown in Table 4. Both tables can be saved as an Excel table file or printed directly. The VOLVN model provides a script file when running with AutoCAD software, the blasting passport will be drawn automatically in seconds, the obtained passport is shown in Figure 6. The VOLVN model was tested by One Member Limited Song Da 10.1 Company in the construction of DakMy3 hydropower project. The application of the model has produced good results, with the drillhole utilization coefficient up to 95%, the tunnel boundary was created very well and satisfied all of the investor requirements.

J. Cent. South Univ. (2021) 28: 100−111

104

Figure 5 Introducing initial data Table 3 Table of blasthole profiles

Hole number

Amount of holes

Hole length/m

Charge per hole/kg

Charge length/m

2÷17 16 3.60 1.8 2.250

18÷47 30 3.35 1.6 2.000

49÷54 6 3.35 1.6 2.000

48, 55 2 3.35 1.6 2.000

56÷63 8 3.35 1.5 1.8750

64÷75 12 3.35 1.5 1.8750

Sum 75 255.50 114.5 150.750

2.5 Comparison with other tunnel blast design models with an example

The comparison is achieved by introducing a similar input data as the blast design example

Table 4 Table of economic-technical indices

Parameter Value

Rock coefficient, f 7

Area of excavation/m2 36.175

Area of used section/m2

Average depth of holes/m 3.35

Hole utilization coefficient, η 0.896

Specific explosives AD1 for a cycle/kg 114.5

Specific explosives calculated for 1 m of tunnel/(kgꞏm−1)

38.167

Specific detonators required for one cycle 75

Specific detonators required for 1 m of tunnel/m−1 25

Actual specific charge/(kgꞏm−3) 1.055

Material stemming volume/m3 0.1188

Actual face advance for a cycle/m 3

Exploded rock volume for a cycle/m3 108.526

Specific detonators for 1 m3 exploded rock/(kipꞏm3) 0.691

Specific drilling for 1 m of tunnel/m−1 85.167

Specific drilling for 1 m3 exploded rock 2.354

realized with the NTNU model [9] and the Swedish model [12], the main input is as follows: tunnel area=19.5 m2, drillhole diameter=45 mm, drillhole length=3.2 m, empty hole diameter=102 mm, explosive type=cartridge explosive, explosive density=1200 kg/m3, rock constant=0.4. The rock constant c=0.4 is assumed to be equivalent to the rock Protodyakonov coefficient f=10 and the cracks’ distance=0.7 m. The blasting result is shown in Table 5. A comparison of total blast design result between NTNU model, Swedish model and VOLVN model is summarized in Table 6.

Figure 6 Blasting passport in AutoCAD (Length unit: mm)

J. Cent. South Univ. (2021) 28: 100−111

105

Table 5 Blast design result realized by VOLVN model

Parameter Value

Rock coefficient, f 10

Area of excavation/m2 19.516

Area of used section/m2

Average depth of holes/m 3.2

Hole utilization coefficient, η 0.938

Specific explosives AD1 for a cycle/kg 96.3

Specific explosives calculated for 1 m of tunnel/(kgꞏm−1)

32.1

Specific detonators required for one cycle 45

Specific detonators required for 1 m of tunnel/m−1 15

Actual specific charge/(kgꞏm−3) 1.645

Material stemming volume/m3 0.02445

Actual face advance for a cycle/m 3

Exploded rock volume for a cycle/m3 58.548

Specific detonators for 1 m3 exploded rock/(kipꞏm3) 0.769

Specific drilling for 1 m of tunnel/m−1 48

Specific drilling for 1 m3 exploded rock 2.46

Table 6 Total blast design results

Item NTNU model

Swedish model

VOLVN model

Total number of blastholes 45 40 45

Specific drilling/(mꞏm−3) 2.5 2.2 2.46

Specific charge/(kgꞏm−3) 1.7 1.9 1.65

3 Results of investigation on contour

blasting parameters by using VOLVN model

In order to investigate the relations among rock Protodyakonov coefficient, cracks’ distance and total blastholes number, specific charge with

the variation of blasthole diameter and the tunnel area, the following input parameters are the same in all of the automatic calculated processes: 1) Tunnel section shape: semi-circular with a width/height ratio of 1.5; 2) Number of empty holes for parallel methods: one 102 mm hole per each cut; 3) Explosive type: Ammonite AD1 with the following characters: lead bomb expansion of (detonating pressure) 0.972 cm3, explosive speed of 0.857 m/s, specific gravity of 0.905 kg/m3. 4) The face advance of one tunneling cycle is 3 m. 3.1 Relation between rock Protodyakonov

coefficient and specific charge The relation between rock Protodyakonov coefficient (f) and specific charge (Sc) with the variation of tunnel area (A) was investigated by following procedures: 1) Varying the value of rock Protodyakonov coefficient and tunnel area; 2) Fixing diameter of charge drillhole: d= 38 mm; 3) Fixing cracks’ distance value: dc=0.7 m. The calculated results are shown in Table 7 and Figure 7. The equations that present the relation between them are shown in Table 8. The relation between rock Protodyakonov coefficient (f) and specific charge (Sc) with the variation of charged drillhole diameter (d) was investigated by following procedures: 1) Varying the value of rock Protodyakonov coefficient and charged drillhole diameter; 2) Fixing value of tunnel area: A=37.5 m2;

Table 7 Relation between rock coefficient (f) and specific charge (Sc) with variation of tunnel area

f Sc/(kgꞏm−3)

13.5 m2 19.5 m2 24.0 m2 37.5 m2 54.0 m2 73.5 m2 96.0 m2 110.0 m2

3 1.164 0.891 0.805 0.744 0.652 0.582 0.568 0.569

5 1.426 1.1 0.991 0.915 0.815 0.724 0.698 0.698

7 1.703 1.308 1.174 1.073 0.931 0.827 0.798 0.798

9 1.903 1.473 1.278 1.193 1.012 0.898 0.868 0.876

11 1.983 1.523 1.337 1.246 1.049 0.93 0.897 0.917

13 2.079 1.581 1.419 1.29 1.121 0.996 0.965 0.965

15 2.156 1.655 1.513 1.334 1.153 1.021 0.985 0.984

17 2.336 1.742 1.563 1.423 1.237 1.099 1.05 1.065

19 2.44 1.855 1.666 1.519 1.323 1.177 1.144 1.145

J. Cent. South Univ. (2021) 28: 100−111

106

Figure 7 Relation between rock strength index and

specific charge with variation of tunnel area

Table 8 Equations of relations between rock strength

index and specific charge with variation of tunnel area

Tunnel area/m2 Specific charge/(kgꞏm−3)

13.5 Sc=0.7708f 0.3917, R²=0.9901

19.5 Sc=0.6013f 0.3827, R²=0.9857

24.0 Sc=0.5392f 0.3818, R²=0.9938

37.5 Sc=0.5086f 0.3685, R²=0.9875

54.0 Sc=0.4504f 0.3588, R²=0.9901

73.5 Sc=0.402f 0.3567, R²=0.9898

96.0 Sc=0.3921f 0.3526, R²=0.9891

110.0 Sc=0.3915f 0.3556, R²=0.9899

3) Fixing cracks’ distance value: dc=0.7 m. The calculated results are shown in Table 9 and Figure 8. The equations that present the relation between them are shown in Table 10. 3.2 Relation between cracks’ distance and

blasting result parameters The effect of cracks’ distance (dc) on drillholes number (N) and specific charge (Sc) with the variation of tunnel area (A) was investigated by the following procedures: 1) Varying the value of cracks’ distance and tunnel area; 2) Fixing diameter of charge drillhole: d= 38 mm; 3) Fixing rock Protodyakonov coefficient value: f=7. The calculated results are shown in Table 11, Figures 9 and 10. The equations that present the relation between them are shown in Table 12. The effect of cracks’ distance (dc) on drillholes

Table 9 Relation between rock coefficient and specific

charge with variation of charged drillhole diameter

Rock coefficient

Specific charge/(kgꞏm−3)

38 mm 45 mm 51 mm 64 mm

3 0.744 0.761 0.788 0.91

5 0.915 0.937 0.99 1.158

7 1.073 1.081 1.206 1.355

9 1.213 1.239 1.365 1.593

11 1.246 1.294 1.422 1.665

13 1.29 1.319 1.526 1.798

15 1.334 1.39 1.627 1.874

17 1.423 1.494 1.716 1.982

19 1.519 1.565 1.78 2.046

Figure 8 Relation between rock coefficient and specific

charge with variation of charged drillhole diameter

Table 10 Equations of relations between f and Sc with

variation of charged drillhole diameter

Drillhole diameter/mm Specific charge

38 Sc=0.5717f0.4423, R²=0.9925

45 Sc=0.4952f0.4411, R²=0.9928

51 Sc=0.5111f0.3797, R²=0.9887

64 Sc=0.5099f0.3682, R²=0.9834

number (N) and specific charge (Sc) with the variation of charged drillhole diameter (d) was investigated by following procedures: 1) Varying the value of cracks’ distance and charged drillhole diameter; 2) Fixing value of tunnel area: A=37.5 m2; 3) Fixing rock coefficient value: f=7. The calculated results are shown in Table 13, Figures 11 and 12. The equations that present the relation between them, are shown in Table 14.

J. Cent. South Univ. (2021) 28: 100−111

107

Table 11 Relation between dc and N, dc and Sc with variation of tunnel area

Cracks’ distance/

m

13.5 m2 19.5 m2 24.0 m2 37.5 m2 54.0 m2 73.5 m2 96.0 m2 110.0 m2

N Sc/

(kgꞏm−3) N

Sc/ (kgꞏm−3)

N Sc/

(kgꞏm−3) N

Sc/ (kgꞏm−3)

N Sc/

(kgꞏm−3) N

Sc/ (kgꞏm−3)

N Sc/

(kgꞏm−3) N

Sc/ (kgꞏm−3)

0.2 40 1.394 44 1.073 50 0.989 68 0.875 82 0.736 102 0.678 125 0.654 140 0.631

0.4 44 1.602 47 1.178 51 1.045 70 0.932 86 0.8 110 0.758 139 0.739 148 0.687

0.6 46 1.676 50 1.26 56 1.153 74 0.985 97 0.907 117 0.808 149 0.793 162 0.754

0.8 47 1.74 51 1.308 57 1.195 79 1.074 103 0.981 129 0.906 162 0.876 175 0.826

0.9 47 1.74 52 1.334 58 1.216 82 1.13 110 1.049 137 0.964 172 0.931 188 0.89

1.0 48 1.81 54 1.414 62 1.329 85 1.177 113 1.094 149 1.065 179 0.985 201 0.961

1.1 48 1.81 57 1.496 64 1.373 85 1.177 115 1.113 152 1.086 188 1.031 212 1.017

Figure 9 Relation between dc and N with variation of

tunnel area

Figure 10 Relation between dc and Sc with variation of

tunnel area

3.3 Relation between tunnel area and blasting result parameters

The effect of tunnel area on drillholes number and specific charge with the variation of charged drillhole diameter was investigated by the following

procedures: 1) Varying the value of tunnel area and charged drillhole diameter; 2) Fixing cracks’ distance value: dc=0.7 m; 3) Fixing rock Protodyakonov coefficient value: f=7. The calculated results are shown in Table 15, Figures 13 and 14. The equations that present the relation between them are shown in Table 16.

4 Analysis of results All achieved results were investigated for tunnel contour blasting passport. Figures 7 and 8 show that specific charge increases as rock Protodyakonov coefficient increases. This increase can be divided into 2 segments: specific charge increases rapidly with rock blastability class I, II, III (f≤9) and increases slowly with rock blastability class IV, V (f>9). Figures 9 and 10 show that drillhole numbers and specific charge increase as distance between cracks on tunnel face increases in all tunnel area dimensions; Figure 9 shows that the line correlated with large area (A≥54 m2) is more inclined than the line correlated with small area (A<54 m2). This means cracks’ distance is an important parameter to take in account of determining the number of drillhole on the tunnel face, especially for large tunnel area. Figures 11 and 12 show that when the cracks’ distance increases, not only the drillhole numbers increase, but also the specific charge needs to increase too, especially for small charged drillhole diameters. Figure 13 shows that the drillhole numbers increase almost linear in function with tunnel area.

J. Cent. South Univ. (2021) 28: 100−111

108

Table 12 Equations of relation between dc and N, dc and Sc with variation of tunnel area

Tunnel area/m2 Drillholes number Specific charge

13.5 N=−10.879dc2+22.401dc+36.272, R²=0.9809 Sc=−0.4453dc

2+1.0056 dc+1.2319, R²=0.9701

19.5 N=3.4091dc2+8.396dc+42.662, R²=0.964 Sc=0.1197dc

2+0.2677dc+1.0314, R²=0.9716

24.0 N=8.9277dc2+3.6449dc+ 48.872, R²=0.9619 Sc=0.1962dc

2+0.1584dc+0.9542, R²=0.9716

37.5 N=6.2565dc2+12.877dc+64.602, R²=0.9824 Sc=0.073dc

2+0.2698dc+0.8133, R²=0.984

54.0 N=2.8352dc2+35.796dc+73.579, R²=0.9854 Sc=0.0169dc

2+0.4207dc+0.6436, R²=0.9928

73.5 N=36.521dc2+9.8891dc+98.919, R²=0.9902 Sc=0.2552dc

2+0.1307dc+0.6478, R²=0.9876

96.0 N=19.349dc2+43.36dc+116.51, R²=0.9972 Sc=0.1332dc

2+0.2393dc+0.6072, R²=0.9966

110.0 N=59.837dc2+2.2826dc+137.44, R²=0.9973 Sc=0.2845dc

2+0.055dc+0.6129, R²=0.9972

Table 13 Relation between dc and N, dc and Sc with the variation of charged drillhole diameter

Cracks’ distance/m

38 mm 45 mm 51 mm 64 mm

N Sc/(kgꞏm−3) N Sc/(kgꞏm−3) N Sc/(kgꞏm−3) N Sc/(kgꞏm−3)

0.2 68 0.875 54 0.889 45 0.958 41 1.250

0.4 70 0.932 56 0.946 47 1.051 42 1.340

0.6 72 0.958 57 0.978 49 1.112 43 1.415

0.8 79 1.074 64 1.117 54 1.181 44 1.438

0.9 82 1.130 66 1.152 54 1.257 44 1.438

1.0 85 1.177 68 1.203 55 1.279 44 1.448

1.1 85 1.177 68 1.203 55 1.293 44 1.483

Figure 11 Relation between dc and N with variation of

charged drillhole diameter

The number of blasthole with small diameter is found to be high. From technical point of view, the results show that it is better to use blastholes with larger diameter for bigger tunnel face areas. Figure 14 shows that specific charge decreases as tunnel area increases, the specific charge is changing abruptly when A≤54 m2, lightly when A>54 m2; and the specific charge value is almost merged at a point when A=110 m2. It means the specific charge value of very large tunnel does not depend on drillhole diameter parameter.

Figure 12 Relation between dc and Sc with variation of

charged drillhole diameter

With the increase of drillhole diameter, the number of drillholes decreases (Figures 11 and 13) while specific charge increases (Figures 8, 12, and 14).

5 Discussion This study has been provided with equations and graphs that can be used in primary blasting passport design. During analysis, some parameters are assumed to be constant. Semi-circular tunnel

J. Cent. South Univ. (2021) 28: 100−111

109

Table 14 Equations of relation between dc and N, dc and Sc with variation of charged drillhole diameter

Drillhole diameter/mm

Drillhole number Specific charge

38 N=−48.813dc3+106.72dc

2−47.823dc+74.023, R²=0.987 Sc=−0.64dc3+1.392dc

2−0.5283dc+0.9372, R²=0.9812

45 N=−47.531dc3+100.49dc

2−45.168dc+59.748, R²=0.9781 Sc=−0.7955dc3+1.6603dc

2−0.6377dc+0.963, R²=0.9831

51 N=−33.59dc3+62.352dc

2−20.722dc+47.021, R²=0.984 Sc=−0.1581dc3+0.2637dc

2+0.2662dc+0.8996, R²=0.9884

64 N=−5.9136dc3+7.4914 dc

2+2.2304dc+40.294, R²=0.995 Sc=0.5062dc3−1.2427 dc

2+1.1267dc+1.0669, R²=0.9888

Table 15 Relations between A and N, A and Sc with variation of charged drillhole diameter

Drillhole diameter/

mm

13.5 m2 19.5 m2 24.0 m2 37.5 m2 54.0 m2 73.5 m2 96.0 m2 110.0 m2

N Sc/

(kgꞏm−3) N

Sc/ (kgꞏm−3)

N Sc/

(kgꞏm−3) N

Sc/ (kgꞏm−3)

N Sc/

(kgꞏm−3) N

Sc/ (kgꞏm−3)

N Sc/

(kgꞏm−3) N

Sc/ (kgꞏm−3)

38 46 1.603 51 1.308 56 1.174 79 1.073 98 0.931 118 0.827 151 0.815 169 0.798

45 39 1.869 45 1.551 47 1.273 62 1.081 76 0.946 95 0.851 111 0.818 125 0.807

51 44 1.490 54 1.206 66 1.026 77 0.914 99 0.87 106 0.814

64 42 1.355 46 1.097 54 0.967 61 0.912 64 0.828

Figure 13 Relations between A and N with variation of

charged drillhole diameter

Figure 14 Relations between A and Sc with variation of

charged drillhole diameter

shape is chosen to investigate the relations between blasting parameters because it is a popular tunnel shape in situ. This relation should have a

Table 16 Equations of relations between A and N, A and

Sc with variation of charged drillhole diameter Blasthole

diameter/mm Number of blastholes Specific charge

38 N=1.2783A+27.692,

R²=0.9977 Sc=3.4345A−0.321,

R²=0.968

45 N=0.8872A+27.59,

R²=0.9981 Sc=4.8406A−0.397,

R²=0.9612

51 N=0.7318A+26.16,

R²=0.9947 Sc=4.989A−0.389,

R²=0.9865

64 N=0.3168A+29.895,

R²=0.9922 Sc=6.3063A−0.431,

R²=0.9782

modification coefficient adequate with tunnel shape. One empty hole of 102 mm diameter is selected for the parallel hole cut method in all calculation process. So, it should be clarified that if another parallel hole cut method is used, the value of drillhole numbers and specific drilling should have a little modification. If explosive detonating pressure increases, the burden also increases. The value of drillhole numbers and specific charges thus will decrease. Consequently, in blasting practice need to multiply research results with an explosive detonating pressure coefficient. 6 Conclusions Model VOLVN for tunnel contour blasting passport design was developed to help in completing an automated closed cycle from calculating parameters to design blasting passport in AutoCAD. The VOLVN model can be used to analyze the effect and the sensitiveness of rock

J. Cent. South Univ. (2021) 28: 100−111

110

Protodyakonov coefficient, distance between cracks on the tunnel face, blasthole diameter and tunnel area on blasting results. Outcomes of the investigations can meet the essential factors such as required specific charge and drillhole number for a blasting design. The results of the analysis show that specific charge increases as rock Protodyakonov coefficient and cracks’ distance increase but specific charge decreases when tunnel face area increases. Moreover, the number of holes increases linearly as tunnel face area increases. The findings demonstrate that with increasing drillhole diameter, the number of drillholes decreases while specific charge increases. This research provides a deep investigation about relation between principal blasting conditions with blasting result parameters in some secondary fixed conditions such as tunnel shape, parallel hole cut method and explosive substance. The model results thus need to be modified the coefficient to achieve optimum blasting pattern in blasting practice.

Contributors CAO Ping provided the concept and edited the paper. Nguyen Ngoc MINH designed the study, conducted the literature review, wrote and edited the paper. LIU Zhi-zhen edited the paper. Conflict of interest CAO Ping, Nguyen Ngoc MINH and LIU Zhi-zhen declare that they have no conflict of interest.

References [1] VERMA H K, SAMADHIYA N K, SINGH M, GOEL R K,

SINGH P K. Blast induced rock mass damage around tunnels

[J]. Tunnelling and Underground Space Technology, 2017, 71: 149−158. DOI: 10.1016/j.tust.2017.08.019.

[2] MISHRA A K, GUPTA R N. Rapid excavation of tunnels

using innovative drilling and blasting techniques [C]// The 10th International Symposium on Rock Fragmentation by

Blasting. London: Taylor & Francis Group, 2013: 15−22.

[3] HU Ying-guo, LU Wen-bo, CHEN Ming, YAN Peng, YANG Jian-hua. Comparison of blast-induced damage between

presplit and smooth blasting of high rock slope [J]. Rock

Mechanics and Rock Engineering, 2014, 47(4): 1307−1320. DOI: 10. 1007/s00603-013-0475-7.

[4] LIU Kai-yun, LIU Bao-guo. Optimization of smooth blasting

parameters for mountain tunnel construction with specified control indices based on a GA and ISVR coupling algorithm

[J]. Tunnelling and Underground Space Technology, 2017, 70: 363−374. DOI:10.1016/j.tust.2017. 09.007.

[5] MAN Ke, LIU Xiao, WANG Ju, WANG Xi-yong. Blasting

energy analysis of the different cutting methods [J]. Shock

and Vibration, 2018, 2018: 9419018. DOI: 10.1155/2018/ 9419018.

[6] XIE L X, LU W B, ZHANG Q B, JIANG Q H, WANG G H,

ZHAO J. Damage evolution mechanisms of rock in deep tunnels induced by cut blasting [J]. Tunnelling and

Underground Space Technology, 2016, 58: 257−270. DOI:

10.1016/j.tust. 2016.06.004. [7] SOROUSH K, MEHDI Y, ARASH E. Trend analysis and

comparison of basic parameters for tunnel blast design

models [J]. International Journal of Mining Science and Technology, 2015, 25(4): 595−599. DOI: 10.1016/j.ijmst.

2015.05.012.

[8] BERTA G. Explosives: An engineering tool [J]. Italesplosive, 1990, 6: 452−460.

[9] Charge calculations for tunnelling [M]// Underground

Mining Methods Handbook. New York: Society of Mining Engineers, 1982.

[10] OLOFSSON S O. Applied explosives technology for

construction and mining [M]. ARLA, Sweden: APPLEX (Applied Explosives Technology), 1990.

[11] ZHOU Chuan-bo, WANG peng, LEI Yong-jian, YIN

Xiao-peng. Optimization on cut-hole of mining tunnel excavation [J]. Mining Science and Technology, 2009, 19(1):

70−73. DOI: 10.1016/ S1674-5264(09)60013-2.

[12] ZARE S, BRULAND A. Comparison of tunnel blast design models [J]. Tunnelling and Underground Space Technology,

2006, 21(5): 533−541. DOI: 10.1016/j.tust.2005.09.001.

[13] JIMERO C L, JIMERO E L, CARCEDO F J A. Drilling and blasting of rocks [M]. London: Taylor& Francis Group,

1995.

[14] ZHANG Zong-xian. Rock fracture and blasting theory and applications [M]. Oxford: Butterworth-Heinemann, 2016.

DOI: 10.1016/b978-0-12-802688 -5.00003-8.

[15] XIAO Shuang-shuang, LI Ke-min, DING Xiao-hua, LIU Tong. Rock mass blastability classification using fuzzy

pattern recognition and the combination weight method [J].

Mathematical Problems in Engineering, 2015: 724619. DOI: 10.1155/2015/724619.

[16] NGUYEN H, BUI X N, TRAN Q H, LE T Q, DO N H, LE T

T H. Evaluating and predicting blast-induced ground vibration in open-cast mine using ANN: A case study in

Vietnam [J]. SN Applied Sciences, 2019, 1(1): 125. DOI:

10.1007/s42452-018 -0136-2. [17] PROTODYAKONOV M. Mechanical properties and

drillability of rocks [C]// Proceedings of the Fifth

Symposium on Rock Mechanics. US: Symposium Publication division, 1962: 103−118.

[18] LU P. The characterisation and analysis of in-situ and blasted

block size distribution and the blastability of rock masses [D]. London: University of London, 1997.

[19] LANGEFORS U, KIHLSTROM B. The modern technique

of rock blasting [M]. Stockholm: Almqvist & Wiksell Forlag AB, 1978.

[20] NOGEL J O. Rock fragmentation with explosives [M]. La

Habana: Felix Varela, 1998. (in Spanish) (Edited by FANG Jing-hua)

J. Cent. South Univ. (2021) 28: 100−111

111

中文导读

基于隧道爆破设计模型的光面爆破参数 摘要：光面爆破效果高度依赖炮孔直径、岩石普氏系数、隧道断面和裂隙与隧道轮廓之间的间距等初

始爆破参数。本文提出一种能够实现 Delphi 程序语言与 AutoCAD 对接的算法，基于提出的算法开发

了一种隧道爆破设计模型。该隧道爆破设计模型能够实现以 AutoCAD 为平台的隧道光面爆破自动设

计。在炮孔直径和隧道断面变化的条件下，研究了岩石普氏系数和裂隙间距对炮孔数量和单位炸药消

耗量的影响，给出了一组高度相关方程。研究结果表明，单位炸药消耗量随着岩石普氏系数、裂隙间

距和炮孔直径的增加而增加，但是随着隧道断面积的增加而减小。此外，炮孔数量随着隧道断面积的

增加呈线性增加，但是随着炮孔直径的增大而减小。 关键词：光面爆破；爆破模型；爆破设计；隧道爆破