Undrained Modulus of Soft Clay Under Triaxial Shear with Two Consolidation Modes

Abstract:

In-situ soft clays are in K₀ consolidation state and present mechanical nonlinearity and anisotropy， However， in laboratory triaxial shear tests isotropic consolidation is usually adopted. At present， there has been no systematic comparison and summary of the differences in the modulus E_u of undrained shear between K₀ consolidation and isotropic consolidation. Three kinds of triaxial shear tests， isotropic consolidation undrained compression （ICUC）， K₀ consolidation undrained compression （ACUC）， and K₀ consolidation undrained extension （ACUE）， were conducted on undisturbed and remolded specimens of Shanghai soft clay. The stress-strain curves， nonlinearity of the undrained modulus E_u and the parameter values of the hyperbolic model are presented and compared. The results show that at the same strain level， the E_u of the ICUC test is close to that of the ACUE test， but larger than that of the ACUC test； The ACUC test and ACUE test have similar initial modulus and failure ratio. Based on the test results and the hyperbolic model， a unified equation of the normalized modulus for the three kinds of undrained shear tests was developed and the parameter values for Shanghai soft clay were summarized.

Key words:soft clay;nonlinearity;undrained modulus;K₀ consolidation