基于有效应力的饱和冻土本构模型与变形机理研究

Loess is widely distributed in the northern seasonal frozen soil area in China. With the increase of engineering construction in the frozen loess area and the wide application of artificial ground freezing technique, the research on mechanical properties of frozen loess becomes increasingly important. This project intends to control the specimen’s stress history and stress state prior to freezing through slurry K0 consolidation sampling method, in order to study the mechanical properties and deformation mechanism of frozen loess. This study includes the following parts: to carry out the control-strain-path test on frozen loess, and conduct quantitative analysis of the temperature, strain rate and confining pressure effect on the properties of frozen loess strength, for evaluating the effective stress of frozen loess; Based on the above test data, the parameters of the solid-liquid multi-phase constitutive model were calibrated, and the existing model was improved by combining the prediction efficiency of the model to establish the solid-liquid multi-phase constitutive model suitable for unfrozen soil and frozen soil; The nondestructive repeatable small-strain stiffness probes of frozen and unfrozen soil are further carried out to accurately and efficiently analyze the influence of temperature, strain rate and confining pressure on the initial stiffness of frozen loess, and to clarify the stiffness formation mechanism of frozen loess. The research of this project will provide the demonstration basis for the solid-liquid multi-phase constitutive model based on effective stress, and provide technical support for the engineering safety design of the loess frozen area and the construction method of artificial frozen wall, which has important academic significance and engineering value.

黄土在我国广泛分布于北方季节冻土区，随着黄土冻区的工程建设增加和人工地层冻结技术的广泛应用，冻结黄土力学性能研究日趋重要。本项目拟通过泥浆侧限固结法制样来控制冻结前试样应力历史和应力状态，研究冻结黄土的力学特性和变形机理，具体内容包括：开展控制应变路径的冻结黄土力学试验，定量分析温度、应变速率和围压对冻结黄土强度性能的影响，评估冻结黄土的有效应力；基于上述试验数据标定固液联合相态本构模型参数，结合模型预测效率改进现有模型，建立适用于非冻土和冻土的固液联合相态本构模型；进一步开展冻土和非冻土的小应变无损可重复刚度试验，准确且高效地分析温度、应变速率和围压对冻结黄土初始刚度的影响规律，阐明冻结黄土的刚度形成机制。本项目研究将为基于有效应力的固液联合相态本构模型提供论证基础，为黄土冻区工程安全设计和人工冻结壁施工方法提供技术支持，具有重要的学术意义与工程价值。

黄土在我国广泛分布于北方季节冻土区，随着黄土冻区的工程建设增加和人工地层冻结技术的广泛应用，冻结黄土力学性能研究日趋重要。本项目通过泥浆侧限固结法制样来控制冻结前试样应力历史和应力状态，研究了冻结黄土的力学特性和变形机理，具体内容包括：开展了控制应变路径的冻结黄土力学试验，定量分析了温度、应变速率和围压对冻结黄土强度性能的影响，评估冻结黄土的有效应力 ；基于上述试验数据标定了固液联合相态本构模型参数，结合模型预测效率改进了现有模型，建立了适用于非冻土和冻土的固液联合相态本构模型；进一步开展了冻土和非冻土的小应变无损可重复刚度试验，准确且高效地分析了温度、应变速率和围压对冻结黄土初始刚度的影响规律，阐明了冻结黄土的刚度形成机制。研究发现，三种制样方法所得试样的刚度表现出非常微小的应变速率效应。压实样和泥浆样的初始刚度随应变速率增加而增大，然而击实样的初始刚度随应变速率增加而减小。这些研究发现将为土工试验研究和工程土性调查中扰动样制样方法的选择提供借鉴；将冻土-未冻土变形机理运用到隧道施工对邻近地下结构的影响研究中，盾构穿越已建地下结构和新开挖地下结构，侧限宽度比、宽度比和开挖距离比都会对地表沉降曲线产生复杂的影响；标定了以有效应力和温度为状态变量的固液联合相态本构的模型参数。本项目研究将为基于有效应力的固液联合相态本构模型提供论证基础，为黄土冻区工程安全设计和人工冻结壁施工方法提供技术支持，具有重要的学术意义与工程价值。