冻融～荷载联合作用下裂隙岩体局部损伤及断裂特性研究

Because of the existence of the initial cracks, the damage and fracture of the jointed rock mass under the combined effect of the freeze-thaw cycles and loads presented the typical "localization "characteristics. This project uses the combination methods of similar model test, theoretical analysis and numerical simulation to study the local damage of the jointed rock mass and its induced material fracture systematically. Firstly, many groups of rocklike material models containing different angles are produced to carry out the freeze-thaw cycles tests and the low strain rate uniaxial loading tests successively, then the mercury injection penetration (MIP), the scanning electron microscopy (SEM) are adopt to measure the micro-fractures of the joint near-tip zone due to the freeze-thaw cycles, and the high speed photography (HSP), the acoustic emission (AE) technology are used to observe the process of the rock mass propagation and fracture synchronously. Then, based on the test and simulated results, the complex relationship between the joint dip angles, the freeze-thaw cycles effects, the external loads and the local damages, fractures are discussed from the theoretical point of view, we put forward the local damage evolution equation of the jointed rock mass on the condition of the freeze-thaw cycles and loads, the joint near-tip field fracture criterion of the ice expansion forces and the external loads. Lastly, the joint near-tip field extension-fracture constitutive model under the combined effect of the freeze-thaw cycles and loads considering the material damage effects are established, this model reveals the internal relations of the rock local damage and materials fracture. It has the important theory value and the practical significance.

因初始裂隙的存在，冻融～荷载联合作用下裂隙岩体损伤、断裂呈现典型"局部化"特征，本项目采用相似模型试验、理论分析与数值模拟相结合方法，系统研究冻融受荷裂隙岩体局部化损伤及其诱发的材料断裂特性。首先，制备多组含不同倾角的类岩石材料试样，先后进行冻融循环、单轴低应变速率加载试验，并在试验过程中，采用压汞试验、扫描电镜分析冻融循环造成的裂隙尖端区微观起裂、扩展特征，采用高速摄影、声发射技术观测外荷载引起的宏观断裂过程。接着，基于试验及数值模拟结果，从理论角度探讨裂隙倾角、冻融循环、外荷载与局部化损伤、断裂的复杂关系，提出冻融～荷载联合作用下裂隙岩体局部损伤演化方程、冰胀力与外荷载联合作用下裂隙尖端区断裂判据。最后，建立了反映材料损伤效应的冻融～荷载联合作用下裂隙尖端区扩展、断裂本构模型，该模型揭示了裂隙岩体局部损伤与材料断裂的内在联系，具有重要的理论价值及现实指导意义。

因初始裂隙的存在，冻融～荷载联合作用下裂隙岩体损伤、断裂呈现典型局部化特征，本项目采用相似模型试验、理论分析与数值模拟结合方法，研究冻融受荷裂隙岩体局部化损伤及其断裂特性。本课题取得了以下成果：. ①裂隙岩体相似材料制备研究；基于相似性原理，对类岩石材料相似模拟进行相似性控制，明确模拟单裂隙岩体常用原材料，并设计多组正交配比方案试验，获得不同配比方案相似性评价参数；最后，通过极差敏感性分析法确定最优配比方案。. ②冻融循环对岩石损伤效应理论表达及方案设计；分析冻融损伤模型理论表达，建立冻融循环造成的高周、低周损伤模型，实现对不同机制下冻融损伤理论表达；同时，结合损伤理论模型涉及到的冻融温度、时长、循环次数等指标确定方法，并提出建议性冻融循环试验方案。. ③冻融过程中裂隙岩体局部化损伤效应及断裂特性试验分析；采用相似材料配制0°、30°、45°、60°、90°单裂隙类砂岩饱和试样，展开10、20、30、50次冻融循环试验，分析裂隙端部在不同倾角、冻融次数下局部化损伤效应规律。并对裂隙岩体在冻融作用下的局部化损伤效应分析，探讨局部化损伤效应造成的端部断裂特性及扩展路径规律。. ④冻融-荷载联合作用下裂隙岩体损伤效应分析；对已完成冻融循环的试样开展单轴加载试验，探讨冻融、荷载与局部化损伤复杂关系，提出冻融～荷载联合作用下裂隙岩体局部损伤演化方程，得到反映损伤局部化分区段损伤模型表达式。. ⑤冻融～荷载作用引起不同裂纹分布状态下断裂机理分析；分析冻融、荷载作用下复合裂纹渐进破坏过程及扩展准则，探讨冻融～荷载联合作用下裂隙端部断裂特性，并结合COMSOL多场耦合数值模拟，探讨冻融-荷载作用下的裂隙岩体温度场及冻胀演化过程，建立冻融次数、裂隙倾角与端部断裂应力关联。. 研究成果将对寒区岩体工程建设的安全性与稳定性评价具有重要的现实意义。且对提高人工冻结法凿井、液化天然气地下储气库设计研究也有重要参考价值。