最大吸力历史下原状高液限黏土力学响应及愈合特性研究

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

摘要

【目的】为研究最大吸力历史作用对高液限黏土固结不排水力学特性的影响，通过对原状高液限黏土进行饱和、完全脱湿及再饱和处理，制备具有最大吸力历史作用的试样。【方法】采用三轴剪切试验，对比分析原状试样与经历最大吸力历史作用试样的力学响应，基于破坏模式揭示出高液限黏土愈合特性，并结合微观结构变化予以验证。【结果】结果显示：最大吸力历史作用改变高液限黏土的固结不排水力学特性。在50kPa围压条件下，峰值应力同比增幅达87.5%~171.3%,孔隙水压力峰值同比降幅为16.7%~20%;在50 kPa和100 kPa围压下，表征各向异性的方差值分别从47.1和321,下降至8.2和94.9。试样应力-应变曲线由硬化型转为软化型，孔隙水压力由“先增后不变”转为“先增后降”,有效应力路径由“硬化-剪胀”和“硬化-剪缩”转变为“软化-部分剪缩-部分剪胀”,各向异性程度降低。【结论】结果表明：高液限黏土具有愈合特性，其实现依赖于附加应力作用。该特性促使经历最大吸力历史作用的试样在固结不排水剪切路径下，微观颗粒形态重塑，细观裂隙闭合，最终宏观表现为抗剪强度提升至原状试样的1.2倍~1.3倍。研究成果为高液限黏土地区的工程实践提供理论依据。

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.

关键词

高液限黏土 / 基质吸力 / 应力路径 / 愈合特性 / 裂隙闭合 / 力学特性 / 影响因素 / 固结不排水

Key words

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

基金资助

国家自然科学基金项目(52478354)

安徽省自然科学基金项目(2208085US01)

安徽省自然科学基金项目(2208085US18)

安徽省自然科学基金项目(2308085US03)

安徽省自然科学基金项目(2308085US16)

安徽省自然科学基金项目(2408055US004)

安徽省水科院科技攻关项目(KJGG202302)

安徽省水利科技项目(SLKJ202501-1)

天津市自然科学基金重点项目(25JCZDJC00110)