Investigation of kinematic behavior and earth pressure development of geogrid reinforced soil walls

Geogrid reinforced soil is an advanced composite material that is widely used for the construction of retaining walls as frequently needed in transportation structures. Most standards and proposed design methods have included a beneficial effect of geogrid reinforcement on the earth pressure that acts on the facing of a retaining wall. However, field measurements at applications often show much lower deformations and stresses as estimated from the design. This indicates a certain improvement potential for the design of geogrid reinforced soil structures and thereby for the general acceptance of geogrid reinforced soil. Therefore, at RWTH Aachen University model tests with geogrid reinforced soil retaining walls have been carried out. The design of the developed test apparatus allows the determination of various parameters, such as the determination of the earth pressure distribution at the facing, geogrid connection loads at the facing and specimen deformations throughout the whole cross section of the test wall. This article deals with the results of parametric studies focusing on the reduction of the active earth pressure in geogrid reinforced retaining structures due to geogrids with varying reinforcement ratio, i.e. number of reinforcement layers per specimen height, and reinforcement stiffness. A reduction of the earth pressure due to a surface load was apparent already underneath the topmost reinforcement layer. This effect was observed for both, structures with and without a facing connection of the reinforcement. With increasing reinforcement ratio, the sliding soil wedges decreased in size and only an unconfined soil area, beneath a developing soil arch in between two reinforcement layers, caused a horizontal earth pressure on the facing. All observations were merged to formulate a mechanical model idea that is presented at the end of this article. (C) 2016 Elsevier Ltd. All rights reserved.