结构性黏土扰动劣化过程及微观结构演化机制研究

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

摘要

【目的】结构性黏土在振动扰动作用下的强度劣化及微观结构演化直接影响地基工程的稳定性。为揭示其微观结构演化规律与强度劣化机理，并为地基稳定性分析与控制提供理论与技术支撑，【方法】以湛江组结构性黏土为研究对象，开展室内振动扰动试验，结合无侧限抗压强度试验、扫描电子显微镜(SEM)分析及核磁共振(NMR)技术，探究扰动过程中的土体强度响应与微观结构变化。通过建立累积扰动能量与强度劣化之间的关系，揭示结构性黏土在扰动作用下能量、微观结构和强度演化规律。【结果】结果表明：基于无侧限抗压强度定义的扰动度随累积扰动能量增加呈幂函数式下降趋势，在760.60~3 777.22 J能量区间内表现出显著的破坏敏感性。微观结构分析显示，振动扰动破坏了原有团聚体结构，使土体颗粒排列趋于无序、胶结作用显著减弱，孔隙结构发生重构，表现为团粒孔向粒间孔转化及孔隙率升高。随着扰动累积，颗粒重排、胶结破坏与孔隙重构协同演化，微观损伤不断向宏观强度劣化转化。【结论】累积扰动能量通过破坏团聚体结构、削弱颗粒胶结并重构孔隙形态，加速了结构性黏土强度劣化，形成“扰动—结构破坏—强度劣化”的动态反馈机制。该过程具有明显的累积性与敏感性，对地基稳定性具有显著影响。研究成果可为结构性黏土的扰动敏感性评价及水利工程中地基稳定性控制提供理论依据与技术参考。

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.

关键词

结构性黏土 / 扰动 / 强度劣化 / 微观机理 / 影响因素 / 累积扰动能量 / 核磁共振 / 孔隙结构

Key words

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

基金资助

广西自然科学基金项目(2024GXNSFAA010450)

国家自然科学基金项目(41867035)