Mechanical properties of structured high liquid limit clay under maximum drying stress conditions

The selection of structural strength indicators is of utmost importance for slope engineering safety. This paper, with the backdrop of the destruction of high liquid limit clay layers in the Huai River slope, aims to investigate the influence of dry-wet (D-W) cycles on the structural and mechanical properties of undisturbed high liquid limit clay. Through unconfined compression tests, scanning electron microscopy (SEM) tests, and triaxial shear tests, the structural behavior, stress-strain curves, porewater pressure-strain curves, and effective stress paths of undisturbed samples taken at three different angles and reconstituted samples were analyzed under the condition of maximum drying stress with 0 and 1 D-W cycle. Based on the impact of D-W cycles on the effective stress path, the shear failure mode of structurally high liquid limit clay under the influence of D-W cycles was identified. A method for evaluating the anisotropic level of structural clay after experiencing D-W cycles was proposed. The test results show that compared with reconstructed soil, the undisturbed high liquid limit clay with structure is more significantly affected by the D-W cycle. After D-W cycles, the CU shear strength of high liquid limit clay increased significantly. The failure mode transitioned from a hardening-shear dilation mode to a softening-partial shear contraction-partial shear dilation mode. The appearance of the phase transition state (PTS) point may be attributed to the partial action of effective stress on cracks inside the sample, resulting in shear contraction. D-W cycles weakened the structural properties (anisotropy) of high liquid limit clay.