Relying on the open excavation section of Jiang Bei of the Yangtze River tunnel in Wuhan

a series of drained triaxial tests on unloading stress paths at K0 consolidation have been carried out with undisturbed silty clay. And the deformation characters under unloading were deeply analyzed. Analysis shows that stress-strain curves and stress paths have close relationship and the stress-strain curves under unloading are similar to a hyperbolic type. According to the stress-strain curves

unloading stress paths can be divided into two groups A and B. The stress paths of group A exhibit axial compression and ones of group B show axial tension. The normalization of its stress-strain relationship is very good under unloading stress paths for undisturbed silty clay. The stress-strain curves of different confining pressures in the same stress path can be normalized with average confining pressures. But normalized equations of groups A and B are different. Additionally the normalized equations of all stress paths have been given. This outcome can be used to further research on both deformation parameters and constitutive equation of soils under unloading.