Dynamic Properties of Sand in Constant-Volume and Constant-Load Tests

Constant-volume and constant-load tests were performed on Babolsar and Toyoura sands by using a modified SGI cyclic simple shear device which provides the capability of back pressure saturation. All tests were shear strain controlled and conducted under different values of relative density, vertical effective stress and shear strain amplitude. Results revealed that Dr, σ′v and γ affect shear modulus and damping ratio under both constant-volume and constant-load conditions in similar ways except the shear strain amplitude which has no important influence on damping of constant-volume tests. The effects of Dr, σ′v, γ and the number of cycles on variations of shear modulus and damping ratio of sand were found to be more pronounced under constant-load condition. It seems that the differences between the results may be due to the different fabric produced in two kinds of test samples rather than to the test method. However, further study is needed to clarify this issue