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Execution of part of works on landslide stabilization in the cut zone no. 4 from km 878+675 to km 879+200, Phase II within the E75 motorway construction project, Section: Grdelica (Gornje Polje) – Caričina dolina LOT 1: Road and bridges from Grdelica to the Predejane tunnel (Serbia)

Investor: Koridori Srbije d.o.o. (LLC) Belgrade
Contractor: Integral inženjering a.d. (JSC) Laktaši
Work values: BAM 26.5 million or EUR 13.5 million 

General information about the project:ct:

Corridor 10 is one of the most important pan-European transport corridors passing through Serbia. The program for the construction of Corridor 10 through Serbia is implemented through four projects that are divided into sections, and those into lots (contracts).

The company “Integral inženjering” a.d. (JSC) Laktaši was the main contractor on the section Caričina Dolina – Vladičin Han, LOT 5: Roads and bridges on the subsection Caričina Dolina – Manajle Tunnel.

The contractor on the section Grdelica (Gornje Polje) – Caričina dolina, LOT 1: Road and bridges from Grdelica to the Predajane Tunnel was Joint Venture (JV) AZVI SA (Spain) and TADDEI SpA (Italy).

Due to particularly complex conditions, the investor awarded the company “Integral inženjering” a.d. (JSC) Laktaši the execution of part of works on the rehabilitation of cut 4 on the section Grdelica (Gornje Polje) – Caričina dolina, LOT 1: Road and bridges from Grdelica to the Predajane Tunnel.

The aim of the project is to stabilize upper parts of cuts above the existing supporting structure of micro-piles, starting from the chainage at km 878+675 to km 879+200.

Project solution and content of works:

Within this project, a technical solution has been defined, consisting of unloading by excavation behind the existing structure of micro-piles with simultaneous protection of excavated levels and production of protective structures from piles of diameter of Ø1500 mm.

Unloading by excavation is planned in several levels of a height of about 10 m with a slope of 1:1.2 or 1:1.5, from top to bottom. Between each two levels the platform is planned, of width of about 4.0 to 5.0 m and on each platform there is a channel for drainage of surface water from the slope.

Permanent measures for local stabilization are provided on the front side of each excavated slope. These measures represent flexible systems consisting of steel or composite nets with a dual role for bearing capacity and preventing surface erosion. The nets are fastened to the surface using SN anchors of diameter of Ø=25 mm or with IBO anchors of diameter of Ø=32 mm.

The length of anchors is 9.00 m, 12.0 m or 15.0 m, depending on the degree of degradation. The anchor layout is on a 3.0 x 3.0 m grid, in a zigzag layout.

In addition, this project defines the construction of two protective structures from piles of diameter of Ø1500 mm. These structures are arranged on platforms behind the retaining wall.

The first piles structure is planned on the second berm from below. It consists of two rows of piles in a zigzag arrangement with a pile cap measuring 500/120 cm above piles. The axial distance of piles is 3.0 m in the transverse and 6.0 m in the longitudinal direction.

The second structure is provided on the fourth berm from below and consists of one row of piles at an axial distance of 3.0 m, with a caping beam measuring 200/120 cm above piles. Both structures are planned as concrete structures made of classic concrete of the C25/30 brand reinforced with B500B reinforcement.