Mechanical responses and healing properties of undisturbed high liquid limit clay under maximum suction history

Abstract

[Objective] To investigate the effect of maximum suction history on the consolidated undrained mechanical properties of high liquid limit clay, samples with maximum suction history are prepared through saturation, complete dehumidification, and resaturation of undisturbed high liquid limit clay. [Methods] Triaxial shear tests were conducted to compare and analyze the mechanical responses of undisturbed samples and samples subjected to maximum suction history. The healing characteristics of high liquid limit clay were revealed based on failure modes, and these characteristics were verified by examining changes in microstructure. [Results] The result showed that maximum suction history altered the consolidated undrained mechanical properties of high liquid limit clay. Under a confining pressure of 50 kPa, the peak stress increased by 87.5% to 171.3%, while the peak pore water pressure decreased by 16.7% to 20%. Under confining pressures of 50 kPa and 100 kPa, the variance values representing anisotropy decreased from 47.1 and 321 to 8.2 and 94.9, respectively. The stress-strain curves of the samples changed from a hardening type to a softening type. The pore water pressure response shifted from “first increasing and then remaining constant” to “first increasing and then decreasing”. The effective stress path transformed from “hardening-shear dilation” and “hardening-shear contraction” to “softening-partial shear contraction-partial shear dilation”, and the degree of anisotropy was reduced. [Conclusion] High liquid limit clay exhibits healing characteristics, and the realization of these characteristics depends on the action of additional stress. Under consolidated undrained shear paths, micro-scale particle morphology remodeling and meso-scale fracture closure are promoted in samples subjected to maximum suction history. Ultimately, a macroscopic increase in shear strength of 1.2 times to 1.3 times is exhibited compared to undisturbed samples. A theoretical basis is provided for engineering practice in areas with high liquid limit clay.

Keywords

high liquid limit clay / matrix suction / stress path / healing properties / crack closure / mechanical properities / influencing factors / consolidated undrained