粉质黏土循环浸水强度软化规律研究

Research on the softening law of cyclic immersion strength of silty clay

摘要

【目的】为揭示粉质黏土在循环浸水-风干作用下的强度软化及恢复规律，厘清多次降雨对土体强度软化与边坡变形的影响机制，【方法】通过循环浸水软化试验研究了粉质黏土浸水-风干循环过程中的强度变化特性，并探明其风干阶段的强度恢复规律；结合广西某黏性土边坡降雨变形监测数据，验证多次降雨对边坡变形响应的作用机制；通过构建函数模型与精细化参数赋值方法，实现边坡稳定性动态预测。【结果】结果表明：(1)粉质黏土具有显著循环浸水软化效应，随浸水-风干循环次数增加，其初始黏聚力下降幅度达79%以上，初始内摩擦角亦随之降低，降幅可达47%以上，且再浸水后黏聚力与内摩擦角降至稳定值的时间缩短至原周期的3.6%~10.9%。(2)风干过程中强度恢复呈现三阶段特征：初始阶段(<1 d)黏聚力缓慢下降25.6%,内摩擦角亦随之缓慢下降，降幅为5.4%;中期阶段(1~5 d)黏聚力以0.13 kPa/h的速率增长，内摩擦角则以0.08 kPa/h的速率逐步提升；后期阶段(>5 d)黏聚力的增速明显放缓，降至0.03 kPa/h,而内摩擦角已恢复至天然状态。(3)边坡变形响应时间随降雨次数增加呈指数衰减规律，第3次降雨后变形滞后时间较首次缩短56%,与室内试验强度劣化规律高度耦合。(4)基于损伤累积函数模型与参数动态修正方法，预测的边坡临界降雨次数(N=8±1)与实际失稳工况误差小于10%。【结论】揭示了粉质黏土循环浸水-风干过程的强度演化机制，建立了降雨次数-强度劣化-边坡变形的量化关联模型，提出的动态预测方法为降雨型滑坡应急预警提供了可量化的理论判据，对黏性土边坡防灾体系构建具有重要工程应用价值。

Abstract

[Objective] To investigate the strength softening and recovery mechanisms of silty clay under cyclic wetting-drying actions and clarify the impact mechanisms of multiple rainfall events on soil strength degradation and slope deformation, [Methods] The strength change characteristics of silty clay in the process of water-soaking and air-drying were investigated through the cyclic soaking and softening test, and the strength recovery law in the stage of air-drying was investigated; combined with the monitoring data of the rainfall and deformation of a slope of a clayey soil in Guangxi, the effect mechanism of multiple rainfalls on the response of slope deformation was verified; the dynamic prediction of slope stability was realized through the construction of a function model and the refinement of parameter assignment method. [Results] The result show that:(1) Silty clay exhibits significant cyclic wetting-induced softening effects. With increasing wetting-drying cycles, the initial cohesion decreases by over 79%, while the initial internal friction angle declines by more than 47%. The stabilization time for cohesion and internal friction angle during re-wetting shortens to 3.6%~10.9% of the original duration.(2) Strength recovery during drying displays a three-phase characteristic: in the initial phase(<1 d), cohesion and internal friction angle decrease slowly by 25.6% and 5.4%, respectively; during the intermediate phase(1~5 d), cohesion increases at 0.13 kPa/h and internal friction angle recovers at 0.08 kPa/h; in the late phase(>5 d), cohesion growth rate decelerates to 0.03 kPa/h while internal friction angle fully recovers to natural state.(3) Slope deformation response time follows an exponential decay pattern with rainfall frequency, showing 56% shorter lag time after the third rainfall compared to initial events, which strongly correlates with laboratory-observed strength degradation.(4) The proposed damage accumulation function model with dynamic parameter calibration predicts critical rainfall cycles(N=8±1) for slope instability, achieving less than 10% error compared to actual failure cases. [Conclusion] The research findings reveal the strength evolution mechanism of silty clay under cyclic wetting-drying processes and establishes a quantitative correlation model integrating rainfall frequency, strength degradation, and slope deformation. The dynamic prediction framework provides quantifiable theoretical criteria for emergency early-warning of rainfall-induced landslides, offering significant engineering value for disaster prevention systems in cohesive soil slopes.

关键词

粉质黏土 / 浸水-风干 / 强度恢复 / 函数模型 / 软化效应 / 力学特性 / 边坡

Key words

silty clay / wetting-drying / strength recovery / function model / softening effect / mechanical properties / slope

基金资助

国家自然科学基金项目(42377196)