Experimental evaluation of collpase deformation behavior of a rockfill material

To investigate the saturation induced collapse deformation behavior of rockfill material, a set of large-scale triaxial tests were conducted in saturated and dry-saturated conditions. Specimens were tested under various confining pressures. For dry-saturated tests, specimens were sheared in various stress levels. Results of all dry saturated tests indicate a sudden reduction in the specimen volume during the submerging process. The ratio of the minimum axial strength of a submerged specimen (at the end of the saturation process) to the shear strength of the specimen before saturation is defined as the coefficient of stress recovery, Csr. Results show that this ratio increases as the confining pressure increases, and decreases as the shear stress level increases. According to the results of dry-saturated tests, reduction values of the internal friction angle caused by saturation (??c), the ratio of the elasticity modulus of the material after saturation to its elasticity modulus in dry condition, i.e., Ewet/Edry, and the saturation induced sudden volumetric strain (?vc) decrease as the confining pressures increase. However the shear stress level does not have any meaningful effect on the variation of ??c, Ewet/Edry and (?vc).