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Publicações Técnicas
Alexiew, Dr.-Ing. D.

GEO12-FW-013-HighGeogrid-reinforced Walls with a Flexible Stone-filled Facing in a Mountainous Seismic Region


In the Rhodope Mountain in the south of Bulgaria the route of a national road had to be completely changed due to the construction of a new dam. The new stretch of 11 km crosses mountainous terrain characterized by very steep irregular slopes, varying geological conditions and seismic activity: a challenge from the point of view of environment, geology, seismic resistance, costs, technology and time schedule.

The final optimized solution includes twenty walls from geogrid-reinforced soil (GRS) with a face inclination of 10v:1h and heights of up to 20 m without any berms. These were chosen - among other reasons - due to their high robustness against seismic impact. A special type of thin stone-filled wall facing provided a range of advantages.

The project environment, construction problems and typical solutions are explained, as well as design and calculation philosophy and methods, with typical cross-sections and materials illustrating the specific points. Some important construction related issues and experiences are also reported.


The new Road III-868 from Devin to Mihalkovo in the Rhodope Mountains in southern Bulgaria was a challenge in terms of concept, design, construction, re-design during the construction, time schedule and costs. It crosses a terrain with complex topography and geology in a seismic region. Its length amounts to 11 km comprising one tunnel and twenty geogrid-reinforced almost vertical soil walls of totally 2 km length and up to 20 m height.

A specific type of facing was adopted to fulfil a wide range of requirements.

It was possible to meet all project goals regarding time schedule and costs. The success is based on the one hand on the advantages and flexibility of geosynthetic solutions in geotechnical engineering and on the other hand on the excellent cooperation of all participants: Investor, Consultants, Contractors and Geosynthetic Company.

The road is since summer 2010 (i.e. almost two years) under traffic, the GRS-walls continue to demonstrate an excellent behavior both in terms of stability and low deformability.

This transportation project is may be one of the most distinctive in the region during recent years.