Strength ellipses of induced anisotropy for a compacted sandy material

Abstract

This paper presents a study on strength anisotropy in a sandy material with anisotropic fabric formed by press loading. Two series of DS-CD tests (direct shear tests under CD condition) were performed using a developed DS apparatus with a double-jack system. To maintain anisotropic fabric in a sample, a freezing technique was developed. Shear strength of samples in the active shear zone was found to be stronger than that of the passive zone, and the results could be expressed well by an ellipse equation with tilting coordinates of an angle measuring 15° to the horizontal line. To find a reason for the inclination of the axis of strength ellipses, a 2D-DS test was performed by a developed 2D-DS device. The direction of the main shear zone of a sand sample measuring 15° coincided well with that of the ellipses’ coordinates, which should be taken into consideration when shear strength from a DS-CD test should be used in a safety analysis of a soil structure.