Cyclic deformation characteristics of cement-treated clay were evaluated by conducting a series of hollow cylindrical torsional shear tests. They were also compared with those obtained by relevant cyclic triaxial tests. Due to effects of tensile failure, the equivalent shear modulus in the torsional shear tests degraded at smaller shear strain levels than in the triaxial tests. Such trend of behavior was more significantly observed under smaller confining stresses. In conducting earthquake response analyses of cement-treated ground, such effect of tensile failure shall be properly considered.[This abstract is not included in the PDF]