Abstract
This paper attempts to propose an appropriate technique for precisely estimating in-soil shearing resistance of geogrids based on the test results obtained using two types of direct box shear apparatus. A series of drained direct shear tests changing the configurations of soil and geogrid, roughness of substrate material on which the geogrid is glued, and the distance between the surface of geogrid and the shear plane was performed. Based on the test results, the authors recommend the followings as the appropriate testing method : 1) an apparatus in which normal stress can be applied over a flexible boundary and be measured at the opposite side of the loading system should be used ; 2) the test specimen of the geogrid glued on the substrate should be placed under the sand layer and the surface of the substrate should be installed in a suitable position taking into account potential shear surface ; 3) a suitable substrate material should be used taking into account the mode of interaction between soil and geogrid in situ.
