基于水热力动态耦合的深部粘土层冻结壁变形破坏机理研究

With the deep mining development of coal resource in China，the disasters of freezing shaft sinking in deep alluvium increases continuously,such as the breaking of freezing pipes,the ruptures and water leakage of frozen shaft,and so on. In most cases disasters of deep frozen shafts happen at clay layer stages. In order to explore deformation and failure mechanism of deep frozen wall, and to develop the fundamental theory of deep frozen soil, the researches on the mathematical model for coupled moisture, heat and stress field 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 macro and micro experiments will be carried out on moisture migration under different frozen temperature, temperature gradient and moisture content;the thermal physics and mechanics parameters are obtained by carrying out a series of experiment;the relationships between meso-micro structure evolution and moisture migration and frost heave behavior of frozen clay are established based on the analysis of CT real-time tests and SEM electron microscope scanning; the moisture migration equation is establised based on the dual-porosity medium seepage theory; the yield characteristic and plasticity flow traces are studied, and a generalized elastoplastic constitutive relationship of frozen clay under the condition of loading and unloading is presented; the coupled mathematical model for moisture, heat and stress field is establised by analyzing the couplied mechanism and introducing the moisture migration equation into constitutive relationship,and the the evaluation tool for the stability analysis of frozen soil wall is also presented. 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，冻结管断裂、井壁破裂漏水等事故屡屡发生，其中大部分事故发生在穿越粘土层阶段。为揭示深厚表土冻结壁变形破坏机制，发展和完善深井冻结基础理论，本项目拟以深部冻结粘土为研究对象，采用宏微观结合的方法，研究冻结粘土的水分迁移、温度场与应力场之间的耦合机理。具体内容包括：开展不同冻结温度、温度梯度及含水率下的水分迁移、冻胀的宏微观试验；开展冻结粘土的热物理力学基本参数试验；利用CT与SEM扫描电镜定量研究细微观结构演变与水分迁移、冻胀行为之间的联系；建立深部冻结粘土的双重孔隙介质水分迁移方程；研究冻结粘土的加、卸载屈服特征与塑性流动轨迹，构建深部冻结粘土的本构关系；研究冻结粘土水热力相互作用机理，将水分迁移方程引入到本构关系中，建立冻结粘土的水热力动态耦合理论模型，并基于该模型构建冻结壁稳定性评价工具。通过本研究，对于揭示深部冻结壁的变形破坏机制有重要意义。

随着人工冻结技术在深厚松散土层矿井建设中的广泛应用及凿井深度不断增加，地压力变大，冻结管断裂、井壁破裂漏水等事故屡屡发生，不仅给工程带来安全隐患，影响了井筒的正常施工，而且造成了重大经济损失。本项目拟采用宏微观结合的方法研究冻结粘土的水分迁移、温度场与应力场之间的耦合机理。研究内容与成果主要包括：.（1）深部冻结粘土基本力学特性研究。开展了冻土的基本力学参数试验研究，研究了深部冻结粘土的非线性强度破坏特征；研究了深部冻结粘土非线性变形特征；.（2）研究了深部冻土的流变特征，流变特性可以表现为衰减蠕变和非衰减蠕变两大类。当应力水平较低时表现为衰减蠕变，当超过一定的应力水平，蠕变特性表现为瞬时蠕变阶段、非稳定蠕变阶段、稳定蠕变阶段和渐进蠕变阶段。在此基础上，建立了相应的流变本构关系；.（3）研究了深部冻结粘土的细观损伤特征。通过CT扫描与电镜试验，研究了变形过程的试样内部损伤演化，掌握了冻结过程由于水分迁移等影响；并研究了损伤在加载变形过程中密度损伤与变形之间的关系及冻结后水分迁移造成的体积含水量分布规律；.（4）研究深部冻结粘土水、热、力耦合作用机理。研究基于能量与质量守恒定律，在克拉伯龙方程基础上建立了新的冰透镜体方程，研究了冻结过程中冻结演化规律、冻结锋面移动过程及并透镜体分布特征；.（5）建立了双重孔隙介质水、热、力多场耦合模型，并利用该模型计算分析了深井冻结壁温度场、水分迁移场及冻胀的演变规律，开展了冻结壁温度场、水分场及冻胀变形等特征研究；.（6）建立了深井冻结壁变形破坏力学模型，利用该模型研究了立井冻结壁变形破坏的力学机理，该计算结果对于深部立井冻结冻结壁的结构优化具有指导作用。. 该课题的研究将能够促进深部立井冻结工程基础理论的进一步完善，对深部冻结立井的方案设计及工程实施具有一定的指导作用，该理论研究成果还可以应用到其他人工冻结工程。