Asymptotic state model of saturated low liquid-limit clay under partial drainage condition

To investigate the drainage boundary influence on the strength characteristics of saturated clay, triaxial tests of saturated clay under undrainage, partial drainage, and complete drainage conditions are performed by using the GDS-DYNTTS apparatus. The partial drainage tests are conducted by controlling the strain increment ratio of the volume strain to axial strain as a constant value. The drainage boundary effects on the mechanical properties of the saturated clay are investigated considering the pore water pressure, effective stress path, and asymptotic behavior of the effective spherical stress-effective deviator stress plane. The asymptotic state constitutive equations are established by incorporating the strain increment ratio into the stress path constitutive model according to the asymptotic state and dilatancy characteristics of the saturated clay. The rationality of the model is verified by comparison with experimental results for the pore pressure and effective stress path. The experimental data show that the strain increment ratio of the saturated clay ratio should be less than 0.3. The drainage conditions affect the dilatancy of the normal consolidated clay, effective stress path, and shear strength of the clay. An increase in the strain increment ratio corresponds to a decrease in the pore water pressure and the effective stress ratio of the saturated low liquid-limit clay. The saturated clay specimen remains in a critical state for a long period of time when the axial strain of the specimen reaches 3%, and changes in the drainage condition can inhibit or accelerate soil failure.