Laboratory pull-out tests using bamboo and polymer geogrids including a case study

Abstract

This study investigates the interaction between soil and geogrids by using both direct shear and pull-out tests and applied the results to a case study. A polymer geogrid and bamboo grids were used with clayey sand and weathered clay as backfill since these materials are readily available in Thailand. The results indicated that the interaction between soil and reinforcement consists of: (a) the adhesion between soil and reinforcement on the solid surface area of the geogrid; and (b) the bearing capacity of soil in front of all transverse members of the geogrids which behaved as a strip footing embedded in the soil. The proposed design procedure for pull-out resistance agreed fairly well with the laboratory pull-out test results. In addition, it was observed that bamboo grids have higher pull-out resistance per unit area than the polymer geogrids. Moreover, the cohesive fill proved to be quite effective when used with geogrid reinforcement. Finally, the proposed design procedure and test results were applied to a case study on an irrigation canal bank repaired by the Public Works Department of Thailand using cohesive backfill and Tensar SS2 geogrids resulting in much improved slope stability.