Effect of gradation curve and dry density on collapse deformation behavior of a rockfill material

Abstract

Rockfill material, such as other coarse grained materials, undergoes rapid or sudden settlements of relatively large values, without any changes in the applied loads and only because of submerging. In the literature this phenomenon is called collapse deformation. The effects of gradation curve and dry density on the collapse deformation behavior of a rockfill material were explored and the changes in the strength and deformability parameters of this material caused by submerging were determined. Two large scale triaxial equipments with three different sample diameters of 20, 30 and 80 cm were employed and a set of dry-saturated tests were conducted. Specimens with different gradation curves and various initial dry densities were tested. The results indicate that in all of the dry-saturated tests, sudden reductions in the shear strengths and volumes of the specimens were observed during the submerging process. The effects of material maximum particle size, fines content and initial dry density on the value of sudden shear strength reduction, internal friction angle reduction caused by saturation (Δϕc), the change in elasticity modulus of the material due to submerging, i.e., (Ewet/Edry), and also the saturation-induced sudden volumetric strain (εvc) were evaluated and discussed.