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Case Study: Reinforcement Of Slopes Of The Moscow Ring Road With Weld-Free Geocell Geostep®

Site:

Intersection of the Moscow Ring Road and Volokolamsk Highway, Moscow, Russia

Construction period:

April-May 2018

Description:

Embankment of the approach to an overpass with a height of 3 to 12 m with the laying of slopes 1:1.5, sand backfill

Problem:

Intensive erosion of the surface of slopes in the spring, annual correction work

When carrying out earthworks, slope destruction under the influence of erosion processes is almost inevitable. Unfixed backfill soil is easily susceptible to erosion and weathering, which results in slope destruction, slope erosion, and soil landslides.

Using geocells to strengthen slopes is considered to be the most efficient solution to stabilize soil and prevent the development of erosion processes. However, traditional geocells have a significant drawback. The fact that cell walls on the slope are not perpendicular to the horizon leads to partial precipitation of the filler from the cells. As a result, after each rainy season, the filler accumulates at the base of the slope, and voids are formed inside the cells, and therefore a set of corrective works has to be carried out annually.

This problem has been solved with weld-free rolled geocell. The walls of weld-free cells are perpendicular to the horizon, so the filler material is not subject to washing out or emptying from the cells. Therefore, it is not necessary to carry out correction works every year. The height and size of the cells depend on the angle of the slope and have to be selected individually for each project for better performance.

A typical construction for reinforcement of slope not affected by water flows is, generally, identical to reinforcing slopes with traditional three-dimensional geocells. Weld-free rolled geocell is usually laid on a dividing layer of non-woven geotextile, fixed to the surface of the slope using anchors and filled with plant soil, followed by the sowing of perennial grass.

For the case in question, it was required to strengthen the slopes at the intersection of the Moscow Ring Road and Volokolamsk Highway. PRESTORUS proposed its design using the 10 cm high weld-free geocell, filled with crushed stone fraction 20-40 mm reinforced with a bicomponent binder. Thus, the amount of crushed stone used for filling the cells was reduced. The roll length of up to 200 m allowed to strengthen the slope from top to bottom at once, while the width of rolls of 3.2 m helped save on the materials to fasten the sections and made the installation easier for the workers. 

In conclusion, the total cost reduction of the design project amounted to 6%, thanks to savings on protective works. The crushed stone layer’s thickness was reduced from 20 to 15 cm, the cell height reduced from 15 to 10 cm. The operating costs were reduced by 99%, as the design does not need any additional maintenance and correction works. The design also increased the life cycle for additional 12 years.