Large-Scale Prototype Testing of a Composite Geosynthetics Reinforced Earth Structure for Riverbank Slope Protection Using Fine Grained Sandy Soil

Abstract

This paper presents the field evaluation of large scale prototypes of an innovative composite geosynthetic reinforced earth (CGRE) structure as an alternative for the conventional earth retaining structures, hence a green engineering design for riverbank slope protection. This reinforced earth structure comprises of a geogrid that serves as the main reinforcement and the cover of the facing member of the structure; and a geotextile as separator medium between the infill soil and intermediate horizontal gravel drainage. Three large scale prototypes at full, half, and no gravel drainage were built, monitored, and tested. Clayey sand soil was the fill material used and a 3/2” to 2” sub-rounded gravel was used for the drainage and facing members. CGRE prototypes were evaluated in saturated conditions, and tested under incremental surcharge loadings with a total applied stress of 40 kPa. Lateral displacements for every layer of the structure were determined using horizontal rods where readings were taken from line gauges. Results showed that prototypes with gravel drainage displaced lower than the permissible limit of 4.0%. The CGRE prototype with full gravel drainage had the smallest average total lateral displacement of 1.28%. Hence, it had a higher interface friction resistance, and pull-out capacity than the one with less or no gravel drainage. Overall, the incorporation of gravel drainage improved the performance of the reinforced earth system by reducing the lateral movements of the structure. Therefore, the CGRE structure is a viable slope protection alternative even under saturated conditions.