Experimental characterization of deformation, coefficient of earth pressure at rest, stiffness, and contact force distributions of sand during secondary compression and rebound

Abstract

This paper aims to provide a comprehensive picture of the sand responses during secondary compression and rebound based on experimental characterizations. The experiment was carried out on dry Leighton Buzzard sand using a modified direct shear box equipped with tactile pressure sensors for the stress measurements and bender elements for stiffness (i.e., Ghvand Ghh) monitoring. It was found that secondary compression and rebound followed the same deformation trends as primary compression and rebound to continuously contract and expand, respectively. The deformation characteristics determined the changes in the associated soil properties; therefore, the opposite soil behavior during secondary compression and rebound was observed. During secondary compression, the corresponding void change, deviatoric strains εq, and the deviatoric strain rate [Formula: see text] increased with increasing vertical stress [Formula: see text] or deviatoric stress q because the sample crept more easily under a higher [Formula: see text] or q. The compression deformation gave rise to an increase in the horizontal stress [Formula: see text] and associated coefficient of earth pressure at rest K0. The soil stiffness also increased as the contact normal forces became more homogenized. During secondary rebound, the sample expanded unabated no matter whether [Formula: see text] was greater or smaller than [Formula: see text]. The corresponding void ratio change, εq, and [Formula: see text] increased with decreasing [Formula: see text] or q because the sample expanded more easily under a lower [Formula: see text] or q. The expansion gradually reduced [Formula: see text] along with the associated K0value. The sample stiffness continued to decrease, and contact force homogenization was not observed.