Experimental Study on the Effect of Coexistence of Clay and Silt on the Dynamic Liquefaction of Sand

In order to study the effect of coexistence of clay and silt on the dynamic liquefaction of sand under different void ratios, the characteristics of sand with two different fines contents (FC = 5% and 10%), three different clay silt ratios (CS = 0.25, 1 and 4) under two different void ratios were investigated by the cyclic undrained triaxial test. The test results show that dynamic test results of specimens with different FC, CS and void ratios are different. Liquefaction happens for all specimens and there are two liquefaction types: flow liquefaction (brittle failure) and cyclic mobility (ductility failure). With the increase of FC or CS, two liquefaction types change mutually. When FC is same, the liquefaction resistance of specimens (with different CS) is different. When FC is different, the liquefaction resistance is different with the monotonous change of clay or silt content in fines. When the void ratio is different, the dynamic strength of specimens is different with same FC and CS. The clay and silt play roles of filling, lubrication, bonding and skeleton effect on the sand particles. With the change of clay and silt content in fines, the proportion of four roles is different under different fines content.