Damage constitutive model of sand based on synchronized electrical parameter testing

The development of soil damage leads to strength deterioration of soil and significantly affects its mechanical response. Triaxial compression tests with synchronized electrical resistivity measurements and computed tomography (CT) scanning were conducted to investigate the variations in electrical resistivity, deformation, and strength of sand with different moisture contents under various confining pressures. A damage variable evaluation index was proposed based on the results of electrical resistivity measurements during triaxial compression. The damage evolution process was further analyzed by comparing the pore structure and fractal dimension obtained from CT scans. Based on the disturbed state concept, the classical Duncan-Chang model and the ultimate stress model were employed to describe the relatively intact state and fully adjusted states of sandy soil, respectively, a damage-disturbance nonlinear elastic constitutive model for medium sand was established. The results show that the damage development can be divided into two stages: a micro-damage stage and an accelerated damage stage. The damage variable increases following a power-law trend with axial strain, being consistent with the variation of the fractal dimension obtained from CT scans, confirming the effectiveness of electrical resistivity as an indicator for characterizing the damage evolution of sand. Compared with the Duncan-Chang model, the stress-strain curves predicted by the proposed damage-disturbance constitutive model are more consistent with the experimental data, especially in accurately characterizing the strain-softening behavior under large strain conditions. The findings provide a valuable reference for the application of electrical testing techniques in elucidating damage-evolution mechanisms in geotechnical materials.