133

Ing.Teodor Burilescu, Ing. Ioan Lungu, Ing. Petre Uţă

S.C. Road Consulting & Design S.r.l, S.C. IPTANA S.A., S.C. Geosond S.A.

STABILIZATION AND CONSOLIDATION OF SLOPES IN SUB-ALPINE

AREAS THROUGH CLASSIC AND SELF-DRILLING ANCHORS

Abstract: This article deals with presentation of executing one of jobs in sub-alpine areas of

stabilization slope using two common technologies. Aim of the article is to show advantages and

disadvantages of both technologies.

Profile selfdrilling bars are starting to be used more often in the geotechnical field, mainly

because of the superior advantages towards the classic techniques in certain field conditions, out

of which the most important (in the road building field) are:

• smaller dimensions of the necessary workbenches

• faster execution time

• high flexibility given by the possibility to adjust the lengths of the rods depending on

local events that may appear during execution

• easy access in difficult reachable areas.

Due to these advantages it was possible to solve the high risk instability phenomena for which we

will present you a project done on national road DN 1 km 114+400 – km 114+800. In this area

the road is built on a slope with a high inclination, aproximative 70°, being framed at digging and

filling with 100 year old supporting walls from solid rock stones. The slope consists of sandy

marl slates also known in the specialty paper works as “Sinaia layers”. The layering is almost

done at horizontal level, with a slight downwards inclination due to the bending of the layer

heads and later to the breaking and sliding of the layers downwards. Although this phenomena is

a few centuries old, the activity was slow without any significant changes.

Starting with construction of the road, when the first support stone walls were done (see Figure

1), the phenomena began to intensify and to produce unwanted effects which led to the rebuilding

and consolidation of the existing constructions at least 2 times in the past 80 years.

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The continuous increase of traffic on this road which represents the main arterial road in the

national roads network in Romania had a major influence in the evolution of the instability

phenomena.

In the year 2005, after heavy rains, the phenomena began to intensify even more accelerated, the

movement reaching the speed of 1,5 cm/day. This cause the visible degradation of the

construction and the fast breaking of the road was foreshadowed. (see Figures 2, 3 and 4).

Fig. 1) Old supporting stone wall

Fig. 2) 2005 road situation

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Fig. 3) 2005 road situation

Fig. 4) 2005 Supporting wall situation

The local conditions didn’t allow execution of a temporary solution, and the detours available

were over 200 km long which meant an additional expense for the transport.

At that moment a decision was made to urgently start consolidation of the supporting wall, and

the solution accepted consisted of using of micropiles and selfdrilling (see Figure 5).

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Fig. 5) Micropiles and self-drilling anchors

Taking advantage of the opportunity risen, it was proposed also to make an adjustment to the

route because it was with a lot of curbs and narrow platform 7.00m (see Figure1).

The choosen solution took into consideration both the digging and the filling, and was built from

(see Figures 2 and 3):

1. At digging : Partial rebuilding of the supporting wall, coating with reinforced concrete of

the remaining segment and anchoring the structure with one or two rows of bars type

40/16 depending on the position in the design. The lengths were between 9.00m and

18.00m (see Figure 6).

2. At filling, because road was widened and the sliding plane was under the foundation of

the existing constructions at a depth of 3.00m ÷ 3.50m, it was done a coating with

reinforcement concrete with variable thickness from 0.50m to 0.80m and a cantilever also

variable between 1.50m and 2.00m (see Figure 7).

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Fig. 6) Changes made at digging

Fig. 7) Coating with reinforcement concrete

For the new structure for the filling there were used vertical micropiles to support the vertical

loads and partially the horizontal ones as follows:

• one row of micropiles at the base of the existing wall which was used as a base for the

coating, with the length of 12.00m (see Figure 8).

• one row of micropiles through the old structure of the supporting wall, which contributed

at the reinforcement of the old structure to which the coating concrete bonded.

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Fig. 8) First raw of micropiles from the base of existing wall

All micropiles were done with bars type 52/26 and their length was of 18.00m.

• in the areas with cantilevers, there were used bars 18.00m lengths in dimensions of 40/16

or 52/26 depending on position from the design.

The project used 6.400 lm of different selfdrilling anchors and a volume of aproximative 900m3

of reinforced concrete.

The job was done without stopping traffic, and the execution time was of 4 months. Apart from

the presented project, there were also done 12 columns of ø 1500mm (see Figure 10) anchored, to

replace an arch made from piers that was heavily damaged.

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Fig. 9) Current situation

Fig. 10) Anchored columns

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R=1

50 m

C=7

4mV

= 30k

m/ h

R= -

150

mC

=109

mV

=30k

m/h

R=3

50 m

C=9

9 m

V=5

0km

/ h

R=2

50 m

C=6

0mV

=30k

m/h

i=2.

5%

INCEPUT PROIECT

Km 114+694

Pod

L=48m

Km 115+150

SFARSIT PROIECT Km 115+127

Fig.

1 PL

AN

(TO

P VI

EW)

141

Km

=114

+832

.450

2.5%

2.5%

2.5%

2.5%

142

Km

=114

+871

.071

2.5%

2.5%

2.5 %

2.5 %

2 .5%