Abstract
Shear modulus G of clayey soil at small strain level is discussed in this paper. The authors developed a new direct shear apparatus which is equipped with loadcells inside wall of the shear box and a pair of bender elements (BE) at the top and bottom plates so that mean effective stress σm′ and shear modulus G can be evaluated during consolidation and shear processes of consolidated constant volume direct shear test. Based on the test results, the relationships among void ratio e, mean effective consolidation stress σm′ and shear modules G are compared with the relationships among e, σm′ and Young's modulus E measured by cyclic triaxial loading. A simple equation is proposed based on the observed relationships and it is also shown that the change of G during and after drained creep is due to the combined effects of development ar deterioration of soil structure and change of void ratio. Strong dependency of shear modules G measured by BE during constant volume direct shear test on the effective mean stress σm′ is also found and the relationship between shear strength and shear modules G is discussed.