Mechanical characteristics and microstructure damage evolution of K₀ consolidated soft soil

The effect of K-0 consolidation-induced initial stress anisotropy on the mechanical behavior of soft soil and the evolution patterns of structural damage of soil during triaxial loading were investigated. A series of K-0 consolidated and isotropically consolidated undrained triaxial compression tests were carried out. Microstructural information of specimens was obtained using field-emission scanning electron microscopy and mercury intrusion porosimetry techniques. Results show that K-0 consolidated specimens exhibit higher shear strength and stiffness and lower pore water pressure than the isotropically consolidated ones. The effect of initial shear stress was explored to explain why K-0 consolidation can restrain the build-up of the pore water pressure. Nevertheless, the underlying mechanism is that specimens form a sturdier skeleton after K-0 consolidation characterized by a larger interparticle contact area. The pore size distribution index and shape fractal dimension were used to define damage variables for characterizing microstructural deterioration. The relationship between damage variables and the axial strain can be fitted by an exponential function reasonably well, where the damage increases rapidly before 6% similar to 8% strain. In addition, slip zones with a preferred particle orientation of 30 degrees similar to 50 degrees concerning the horizontal direction appear at shear failure regardless of initial structural states, with which the effective internal frictional angle is closely correlated. The macroscopic mechanical characteristics of soil are subject to microstructural damage and the initial stress anisotropy.