Disturbance-induced degradation process and microstructural evolution mechanism of structured clay

Abstract

[Objective] The strength degradation and microstructural evolution of structured clay under vibrational disturbance directly affect the stability of foundation engineering. The laws governing microstructural evolution and the mechanisms of strength degradation are revealed, and theoretical and technical support is provided for the analysis and control of foundation stability. [Methods] Structured clays of the Zhanjiang Formation were selected as the research object. Laboratory vibration disturbance tests were conducted, in combination with unconfined compressive strength tests, scanning electron microscopy(SEM) analysis, and nuclear magnetic resonance(NMR) techniques, to investigate the strength response and microstructural evolution of the soil during the disturbance process. The relationship between cumulative disturbance energy and strength degradation was established to reveal the evolution laws of energy, microstructure, and strength of structured clay under disturbance. [Results] The result showed that the disturbance degree, defined based on unconfined compressive strength, exhibited a power-law decreasing trend with increasing cumulative disturbance energy, and demonstrated pronounced damage sensitivity within the energy range from 760.60 J to 3 777.22 J. Microstructural analysis indicated that vibrational disturbance destroyed the original aggregate structure, leading to a more disordered arrangement of soil particles, a significant weakening of cementation, and a reconstructed pore structure characterized by the transformation from aggregate pores to interparticle pores and an increase in porosity. With the accumulation of disturbance, particle rearrangement, cementation damage, and pore reconstruction evolved synergistically, leading to the continuous transformation of microstructural damage into macroscopic strength degradation. [Conclusion] Cumulative disturbance energy accelerates the strength degradation of structured clay by destroying the aggregate structure, weakening interparticle cementation, and reconstructing the pore morphology, thereby forming a dynamic feedback mechanism of “disturbance-structural damage-strength degradation”. This process exhibits pronounced cumulative and sensitive characteristics, exerting a significant influence on foundation stability. A theoretical basis and technical reference are provided for evaluating the disturbance sensitivity of structured clay and for controlling foundation stability in hydraulic engineering.

Keywords

structured clay / disturbance / strength deterioration / microscopic mechanism / influencing factors cumulative disturbance energy / NMR / pore structure