路基压实粉质黏土水平残余应力估算方法探讨

Discussion on estimation method of horizontal residual stress of subgrade compacted silty clay

路基填土经压实后会产生残余应力,对路基结构的强度、变形和稳定性影响较大。采用自制的试验装置,开展压实粉质黏土在侧限条件下的水平残余应力测试,分析其随压实度的变化规律;根据反映土体抗剪能力的黏聚力和内摩擦角分量c(x),φ(x)与剪切位移x的非线性关系,基于Mohr-Coulomb准则,提出以黏聚力分量峰值cm及对应内摩擦角分量φf为关键参数的路基压实土水平残余应力分析模型及估算方法,并对估算结果的可靠性进行了误差分析。研究表明:路基压实土产生残余应力的力学实质是紧密接触的土颗粒间存在的摩阻锁固效应,其值随土体压实度提高呈折线型加速增大趋势;土体抗剪能力特征值cm,φf所代表的微剪切变形状态,能较好地反映路基土压实卸荷后微回弹变形条件下的残余应力状态特征;由水平残余应力分析模型获得的计算值与测试数据吻合较好,平均值误差约6.30%;研究成果可为深入分析路基填土压实状态的应力特征和工程性质提供参考。

The residual stress of subgrade soil after compaction significantly affects the strength,deformation and stability of the earth structure. The horizontal residual stress of compacted silty clay under lateral constraints was tested by a self-developed apparatus,and the variation law of the horizontal residual stress with the compaction was examined. Considering the nonlinear relationship between the components of soil cohesion and friction c(x),φ(x),with the shear displacement x,an analytical model,taking the peak value of cohesion component cm and the corresponding internal friction angle φf as the key parameters,was proposed for the prediction of the horizontal residual stress of compacted subgrade soil based on the Mohr-Coulomb criterion.. Finally,an error analysis was performed on the reliability of the calculated results. The research shows that the nature of the residual stress of compacted subgrade soil derives from the inter-particle locking and the residual stress increases as a piecewise function of the soil compaction. The small-shear deformation state represented by the characteristic values of the soil shear capability cm and φf can better reflect the characteristics of the residual stress state under small-rebound deformation condition when subgrade soil is subjected to compaction and unloading. The experimental data and estimated values from the proposed analytical model are in good agreement with an average error of about 6.30%. The research results facilitate a more in-depth analysis of the stress characteristics and engineering properties of compacted subgrade soil.