深部冻土的广义黏弹塑性损伤本构模型及其应用研究

With the deep mining development of coal resource in China，the depth of topsoil with freezing shaft sinking in deep alluvium increases continuously, the traditional mechanics of frozen soil is no longer suitable for the stability evaluation of deep frozen wall. In order to explore deformation and failure mechanism of deep frozen wall, and to develop the fundamental theory of deep frozen soil, the research on the visco-elastoplastic damage constitutive model and its engineering application for deep frozen soil are carried out by employing the method of macro-meso incorporation in local project. This project is concentrated on the following aspects: the relationship between meso-micro damage evolution characteristic and macro mechanics behavior of frozen soil in unloading processes and creep stage after unloading is established based on the analysis of CT real-time tests, and a realistic damage evolution equation is obtained;the yield characteristic and viscous plasticity flow traces are studied, and a generalized visco-elastoplastic damage constitutive model of frozen soil under the condition of unloading is presented in generalized stress space by introducing the theory of damage mechanics based on the hypothesis of damage energy equivalence;in order to describe the deformation behavior of frozen soil under complex stress state, the constitutive model is extended to the complex state by the method of transformation of stress space, and a stability analysis model of deep shaft frozen wall is established.The research has important significance in exploring the deformation mechanism of deep shaft frozen walls, and could provide the theoretical basis for the optimization design and improvement of supporting method.

随着煤炭资源开采不断向深部发展，冻结法凿井穿越表土层厚度不断加大，传统冻土力学理论已不适用于深层冻结壁稳定性评价。为揭示深厚表土冻结壁变形破坏的力学机制，发展和完善深部冻土力学基础理论，本项目拟采用宏、细微观相结合的方法，研究开挖卸荷作用下深部冻土的黏弹塑性损伤本构模型及其工程应用。具体内容包括：开展卸载过程及卸载后蠕变阶段深部冻土的细观损伤CT实时试验，定量研究深部冻土细微观损伤演化与宏观力学行为之间的联系, 建立符合实际的损伤演化方程；研究深部冻土的卸载屈服特征与黏塑性流动轨迹，基于损伤能量等效性假设，构建卸荷条件下冻土的广义黏弹塑性损伤本构关系；采用应力空间变换的方法将本构关系拓展到复杂应力状态，建立深部冻结壁稳定性分析力学模型。通过开展本研究，对于揭示深部冻结壁的变形破坏机理具有重要意义，并为冻结壁的优化设计与支护方式的改进提供理论依据。

随着煤炭资源开采不断向深部发展，冻结法凿井穿越表土层厚度不断加大，传统冻土力学理论已不适用于深层冻结壁稳定性评价。为揭示深厚表土冻结壁变形破坏的力学机制，发展和完善深部冻土力学基础理论，本项目采用了宏、细微观相结合的方法，开展了有关冻土的强度与本构模型方面的研究工作，进行了低温三轴静力试验与流变试验，研究了冻土的强度、弹塑性变形、流变及损伤演化等力学特征，并开展了冻结壁数值模拟优化分析，取得了以下结论：.（1）在低围压下，冻土的应力应变曲线表现为应变软化型，与此对应的体积变形则总是随着轴向应变的增加先缩后胀；而对于高围压下冻土的应力应变曲线表现为应变硬化型，与此对应的体积变形则为压缩型，即体积随轴向应变的增加只是减小，不出现体胀现象。.（2）冻土的强度先是随着围压的增大而增大，而当围压增大到一定值，冻土的强度随围压的进一步增大而减小。为了描述高围压作用下冻土强度随着围压增大而呈现非线性减小的特征，建立了冻土的非线性强度准则。.（3）采用考虑受静水压力影响的偏平面上的破坏形状函数，构建了复杂应力状态下冻土的强度准则，并给出了该强度准则的应力空间破坏曲面。.（4）构建了冻土的广义力学本构关系。体积屈服面采用椭圆的形式，以塑性体积应变为硬化参数；剪切屈服面选用抛物线的形式，以塑性剪应变为硬化参数；引入以塑性体积应变为硬化参数能够反映冻土剪胀性质的抛物线剪胀屈服面。.（5）研究了冻土的宏观变形与微观损伤演化之间的联系。通过对冻土进行CT扫描试验，研究了冻土的应力应变关系及内部结构的损伤演化过程，探讨了温度对冻土的宏观力学性能及微观损伤演化过程的影响。.（6）开展了冻土的流变力学特征。结合损伤力学理论，从冻土内部存在裂隙、空洞等缺陷特征出发，建立了冻土的粘弹塑性损伤本构模型。.（7）建立了深部凿井冻结壁稳定性分析数值计算模型，研究了采用不同冻结壁厚度下冻结壁开挖卸荷冻结壁的变形特征、应力分布等。