The Mechanism of Fabric Changes During Compressional Deformation of Sand

Abstract

ABSTRACT The previous study has shown that the geometrical arrangement of contact surfaces between the grains could have an important bearing on the mechanical properties of granular materials. In an attempt to represent this effect in a quantitative manner, summations of projected areas of contact surfaces of YZ- and XY-planes, being denoted by Sx and Sz respectively, is shown to be an useful index. Particularly, the ratio Sz/Sx which is determined by microscopic analyses of thin sections is believed to be one of the most important fabric features to determine some mechanical properties of granular sands. The ratio Sz/Sx has close relations with mobilized stress ratio as well as dilatancy rate. The maximum value of Sz/Sx at peak stress is determined not only by initial fabric but also by some other properties of granular particles. The process of fabric reconstruction is continuous and no gap can be observed between granular fabrics formed at pre-peak stress and those formed at peak stress. This, continuous reconstruction of the initial fabric with the increase of axial strain is mostly due to the sliding along unstable contacts between grain particles and partly due to the rotation of grain particles.