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

Experiment of the Variation of Shear Strength and Prediction Model of Unsaturated Sandy Soils:Taking the Sandy Soil in Nanchang Area as an Example

为了研究非饱和砂土抗剪强度变化规律并建立有效的预测模型,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,结果表明: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。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。非饱和砂土黏聚力随含水率增大呈先减小后增大的变化规律,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的变化趋势,由干密度变化导致的内摩擦因数变化幅度较小,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。

In order to study the variation of shear strength of unsaturated sandy soils and establish an effective prediction model,taking sandy soils in Nanchang area as the representative,the mechanism of the influence of water content and dry density on the shear strength of unsaturated sandy soils was investigated.The results show that under different water content and dry density conditions,the shear stress-shear displacement curves of unsaturated sandy soils are all of softening type,showing a four-stage nonlinear law of change,which presented a decreasing variability with the change of water content and dry density.The shear strength of unsaturated sandy soils decreases with increasing water content and saturation,which increases with increasing dry density.The cohesion of unsaturated sandy soils decreases and then increases with increasing water content,increasing approximately linearly with increasing dry density.The angle of internal friction increases and then decreases with increasing moisture content,and the change in the coefficient of internal friction resulting from the change in dry density is small,within about 25%.Based on the Moir-Coulomb strength criterion,regarding water content and dry density,a nonlinear regression model of shear strength of unsaturated sandy soils was constructed,which could provide a reference for the selection and prediction of engineering geological parameters.