部分排水时饱和粉质黏土变围压循环三轴试验研究

Cyclic triaxial test on saturated silty clay under partial drainage condition with variable confining pressure

围压循环变化将引起土体孔压累积,加剧土体累积塑性应变,导致地基灾变事故。为研究围压循环变化对饱和粉质黏土变形特性的影响,利用GDS双向振动三轴仪,进行部分排水时饱和粉质黏土的变围压循环三轴试验,研究不同应力路径斜率和循环动应力比时饱和粉质黏土的孔压、轴向累积塑性应变和体应变发展规律,建立部分排水条件时考虑循环围压和循环动应力耦合作用的地基粉质黏土累积应变数学模型。试验结果表明:部分排水时饱和粉质黏土孔压、轴向累积塑性应变和体应变均随循环动应力比和应力路径斜率的增大而增大;动孔压比随着振动次数的增加明显分为急剧增加、快速下降和持续平稳3个阶段;轴向累积塑性应变和体应变均随振动次数的增加而增大。当加载次数超过2 500次时,粉质黏土孔压趋于平稳,变形速率略有降低,但变形持续增加。补充试验结果表明,所建立模型与试验结果具有较高的一致性。研究结果将为交通循环荷载导致的地基灾变控制技术提供理论依据。

The varying cyclic confined pressures will aggravate the pore water pressure and the accumulated plastic strain of soil and even lead to the catastrophic accident.The triaxial tests with cyclic confining pressure were carried out to study the pore pressure,the axial cumulative plastic strain and the volumetric strain of saturated silty clay under different stress paths and cyclic dynamic stress ratios by using GDS triaxial apparatus under partial drained conditions.A mathematical model of accumulated strain for silty clay under cyclic confining pressure and cyclic dynamic stress was established under partial drainage conditions.The experimental results show that the pore water pressure,axial cumulative plastic strain and volumetric strain of the saturated silty clay increase as the cyclic dynamic stress ratio and the stress path slope increases.The dynamic pore pressure ratio versus vibration number curves divided into three stages:rapid increase stage,rapid decline stage and sustained stability stage,respectively.The axial cumulative plastic strain and volumetric strain increase as the vibration number increases.The pore pressure of silty clay tends to be stable,while the deformation rate decreases slightly,but the deformation increases continuously when the number of loading is more than 2 500 times.The supplementary experimental results show that the established model is in good agreement with the experimental results.The results will provide a theoretical basis for the foundation disaster control technology caused by traffic cycle load.