粉质黏土冻土三轴强度及本构模型研究

通过对南京典型粉质黏土?10℃冻土在不同围压、固结方式、应力路径条件下的三轴试验，分析不同因素对三轴强度影响，结果表明：最大轴向偏应力随围压增大而线性增大，且重塑粉质黏土冻土的最大轴向偏应力随围压的增大速度大于原状粉质黏土冻土的增大速度；固结方式对内摩擦角影响较大，对黏聚力影响不大，先等压排水固结再冻结试样强度会大幅度提高；强度和弹性模量受应力路径影响，其中常规加载应力路径强度及弹性模量要大于卸载应力路径强度及弹性模量；基于Duncan-Chang模型建立考虑围压影响的冻结粉质黏土本构模型，参数a、b与围压呈负相关，获得原状粉质黏土以及先等压排水固结再冻结、先等压不排水固结再冻结和先冻结后固结重塑粉质黏土的破坏比均值分别为0.87、0.89、0.93和0.87。

Study on triaxial strength and constitutive model of frozen silty clay

At present, we usually take the soil test samples used in the project on the site and process them into a standard sample in the laboratory, then we freeze samples without pressure and carry out the three axis strength tests. But in the actual engineering, the soil is often frozen under pressures, and few of us have studied the strength differences between the two conditions. There are also few studies on the strength of three axis under different loading methods, so it is necessary to study the stress strain characteristics of Nanjing silty clay under different confining pressures, different consolidation methods and different stress paths. The results show that the maximum axial stress is linearly increased with the confining pressure, and the growth rate of remolded silty clay is larger than that of raw silty clay. The consolidation way has great influence on the friction angle, and less influence on cohesion. The friction angle of frozen remolded silty clay ranged from 21.94 to 28.22. The strength of the isobaric drainage consolidation followed by freezing specimen will be greatly improved; the strength and elastic modulus are affected by the stress path, and the strength and elastic modulus of loading stress path are greater than the unloading stress path. On the basis of Duncan-Chang model, we have established a new model considering the influence of the confining pressures. The damage ratio of the original silty clay and silty clay consolidated by isobaric drainage before freezing, consolidated by isobaric undrained before freezing and consolidated after freezing are 0.87, 0.89, 0.93 and 0.87, respectively.