SLOPE REINFORCEMENT

Geogrids were first used to reinforce soil slopes in Europe in 1980 and then in North America in 1981. The first applications were landslide repairs. In these application the old landslide scarp was excavated and then either a reinforced soil buttress was built to the same geometry or a steepened reinforced soil slope was constructed. Care was taken to make sure deep seated failure surfaces were removed during excavation and that the buttress was placed deep and wide enough to provide adequate slope stability for the finished structure. As this technology was first utilized for landslide repairs in the UK, Ontario, California, and Texas acceptance grew so that it is now commonly used to reinforce and steepen new embankment slopes for roadways, parking areas and commercial building sites. This technology benefits the user in that it creates more useable space at a cost that is often a third to half the cost of conventional alternatives such as use of a retaining walls.


Slope under construction with composite drain Milwaukee,Wi	Finished Slope with erosion mat facing Milwaukee,Wi

Just like with any soil structure the performance of a steepened slope will be directly related to the soil which is used to build it. While geogrids have been used to reinforce highly plastic clays, it is normally done to add safety factor to a stable slope. When designing a reinforced soil slope special attention should be paid not only to the reinfrocement density and soil to be reinforced, but also to the drainage surrounding the structure and erosion protection of the face. The face of a steep slope should be likened to the face of an MSE wall in that it needs to contain the reinforced soil mass. Most steepened slopes utilize a combination of geosynthetic erosion control mats and site specific vegitation. In other cases grout-filled mats, riprap, sloped concrete panels, gabions, hay bales and even mixtures of hay and cow manure wrapped in a geogrid, have been utilized to develop a permanent face.


Finished slope with geogrid wrapped facing La Honda, CA	Finished Slope with sod facing Ocoee,Fl

For the most current information on how to design and specify reinforced slopes refer to Federal Highway Publication No. FHA-SA-93-025, January 1993, Guidelines for Design, Specification and Contracting of Geosynthetic Mechanically Stabilized Earth Slopes on Firm Foundations, Author - Ryan R. Berg, P.E..

FHWA presently has under development a design program and work shop for slope reinforcement under their Demonstration Project No. 82 which is expected to be available in early 1996.

Slope Reinforcement Design Programs are also available from geogrid suppliers, and software suppliers.