基于颗粒流的膨胀土膨胀力时程细观机制研究

Time history micromechanism of expansive soil expansive force based on particle flow simulation

为了深入分析膨胀土在增湿条件下膨胀力时程关系,开展了不同初始含水率和干密度下的无荷膨胀率试验与膨胀力试验,建立了考虑体积应力的膨胀土颗粒膨胀模型;采用颗粒流程序(particle flow code,PFC)数值计算方法,探讨了膨胀力在不同干密度、初始含水率下膨胀力随时间的变化规律,从细观层次上分析了增湿过程中土体接触力链的分布特征,并进行了颗粒膨胀函数中参数对时程曲线的敏感度分析。试验结果表明:增湿过程中膨胀力随时间的增长可以分为快速增长、匀速增长和相对稳定3个阶段。膨胀速率和极限膨胀力均随土体干密度增大而增大,随土体初始含水率的增大而减小。在增湿条件下,膨胀力在0~2 h内基本能达到极限膨胀力的80%。数值计算结果与室内试验结果一致,验证了颗粒膨胀模型的正确性。

In order to deeply analyze the time history relationship of expansion force under humidification conditions,loadless expansion rate test and expansion force experiments under different initial moisture content and dry density is carry out and establish an expansion model of expansive soil particles considering volume stress.Using the particle flow code numerical calculation method,the expansion force at different dry density and initial soil water content is discussed.At the rate,the expansion force changes with time.The distribution characteristics of soil contact force chains in the process of humidification are analyzed at a microscopic level,and the sensitivity of parameters in the particle expansion function to the time history curve is analyzed.The test results show that during the humidification process,the expansion force can be divided into three stages:rapid growth,uniform growth and relative stability.The expansion rate and ultimate expansion force increase with the increase of soil dry density and decrease with the increase of the initial water content of the soil.Under the condition of humidification,the expansion force can basically reach 80%of the ultimate expansion force within 0~2 h.The numerical calculation results are consistent with the laboratory test results,which verifies the correctness of the particle expansion model.