非饱和砂土抗剪强度变化规律与预测模型试验：以南昌地区砂土为例

本文以南昌地区砂土为代表,探讨了含水率、干密度等因素对非饱和砂土抗剪强度影响机理,发现:(1)不同含水率和干密度工况下的非饱和砂土剪应力-剪切位移曲线均为软化型,表现出四阶段非线性变化规律,并随含水率和干密度变化呈现出递变性。(2)非饱和砂土抗剪强度随含水率和饱和度的增大呈减小变化,随干密度增大呈增大趋势。(3)非饱和砂土表现出的黏聚力随含水率增大呈先减小后增大,随干密度增大近似呈线性增大,内摩擦角随含水率增大呈先增大后减小,随干密度变化导致的内摩擦系数变化幅度较小,约在25%以内。基于莫尔-库伦强度准则,构建了考虑含水率和干密度的非饱和砂土抗剪强度非线性回归模型,可为工程地质参数选用和预测提供参考。

Experimental study on the variation law and prediction model of shear strength of unsaturated sand

Taking the sand in Nanchang area as the representative, this paper discusses the influence mechanism of shear strength of unsaturated sand considering the factors of moisture content and dry density, and finds that: (1) The shear stress-shear displacement curves of unsaturated sand under different moisture content and dry density conditions are all softening, showing a four-stage nonlinear change law, and showing progressiveness with the change of moisture content and dry density. (2) The shear strength of unsaturated sand decreased with the increase of moisture content and saturation, and increased with the increase of dry density. (3) The cohesion shown by unsaturated sand first decreases and then increases with the increase of moisture content, approximately linear increase with the increase of dry density, the internal friction angle increases first and then decreases with the increase of moisture content, and the internal friction coefficient changes with the change of dry density is small, about 25%. Based on the Moir-Coulomb strength criterion, a nonlinear regression model of shear strength of unsaturated sand considering moisture content and dry density was constructed, which can provide reference for the selection and prediction of engineering geological parameters.