Strength Anisotropy and Shear Band Direction in Plane Strain Tests of Sand

Abstract

ABSTRACT Strength anisotropy and shear band direction at failure and their relationship for sands were studied experimentally. Using reconstituted specimens of air-pluviated Toyoura sand, plane strain compression (PSC) tests, torsional shear tests and a bearing capacity test with a strip surface footing were performed. Also PSC tests were performed using undisturbed specimens of sand taken from layers in the field, formed by secondary deposition under water. For both types of sands, a significant degree of strength anisotropy was observed. For Toyoura sand, shear band(s) did not appear at a unique angle. That is, in the PSC tests on specimens deposited from the direction, the bedding plane direction differs largely from the zero-extension direction. In this case, shear bands tended to appear in the direction of the maximum stress obliquity plane. This type of shear band appeared also in a model ground loaded with a smooth footing. On the other hand, in the simple shear tests on specimens deposited vertically, the bedding plane direction coincides with the zero-extension direction (i.e, the horizontal direction). In this case, shear bands tended to appear in the the zero-extension direction. In the other cases, shear bands appeared at intermediate directions. The paper discusses also the point that many of the apparent contradictions concerning the shear band direction reported in the literature may be explained, at least partly, by taking into account the relative direction of bedding plane in each case.