正断型隐伏地裂缝破裂扩展综合效应研究

The number of buried ground-fissures is much more than that of exposed ones which have brought about great hazards attractd by more people. So we must face and solve the problems to reduce the potential hazards caused by buried ground-fissures which are probably exposed to ground. There are some studies on the rupure propagation of arctive fault or ground-fissure by model tests, but many of the results of tests are different from the phenomena observed in-site by exploratory trenches across the fault or ground-fissure. This project will research on the rupure propagation of normal buried ground-fissure which is the major type of ground-fissure. Ten operating modes of physical model tests will be carried out to simulate the evolution of rupture propagation along buried ground-fissure towards the overlying soil. In the tests such factors will be considered as the displacement, dip and activity rate of fissure, the thickness and properties of overlying soil and the leakage of surface water to study on the comprehensive effects of rupture propagation and such contents be monitored as stress, displacement and evolution of the rupure propagation to learn about the mechanical stye of all ruptures appeared in the soil during tests. Then the modes of rupture propagation will be summed up after finishing the physical model tests, numerical simulatiion, field investigation of ground-fissures and in-site exploration across ground-fissures. Finally the width of rupture zone of different depth and the largest displacement on surface produced by buried ground-fissure will be caculated according to the nonlinear fracture mechanics, soil mechanics and dislocation theory. To research on the effects on rupture propagation of normal buried ground-fissure has theoretical and practical significance to explain actural ground-fissure geological phenomena and to prevent ground-fissure hazards.

日益增多的地裂缝灾害受到人们的普遍关注，而隐伏地裂缝数量更加巨大，其破裂扩展的随机性及潜在的灾害效应是我们必须面临和解决的问题。基于隐伏地裂缝主要表现为正断型式和一些模型试验结果与大量的活断层和地裂缝实际破裂剖面不一致的事实，本项目将以正断型隐伏地裂缝为对象，通过与实际正断型隐伏地裂缝边界条件接近的物理模型试验，开展受地裂缝位错量、裂缝倾角、活动速率、上覆土层厚度、土层性质和表水下渗等因素影响的隐伏地裂缝破裂扩展综合效应研究，分析其控制性和敏感性因素；通过应力、变形监测和破裂现象观察，确定不同阶段各破裂的力学性质；结合地裂缝的野外调查、勘探和数值模拟试验结果，总结隐伏地裂缝的破裂扩展过程和模式；基于非线性断裂力学、土力学和位错理论，分析破裂扩展的力学作用综合机制，解析不同深度破裂影响带宽度和地表最大位错量，为解释实际地裂缝破裂现象和防治地裂缝灾害提供依据，从而具有理论和实际工程意义。

日益增多的地裂缝灾害受到人们的普遍关注，而隐伏地裂缝数量更加巨大，其破裂扩展的随机性及潜在的灾害效应是我们必须面临和解决的问题。本项目以正断型隐伏地裂缝为对象，通过野外调查、综合勘探、土工试验、物理模型试验、数值模拟和理论分析，开展了北京和汾渭盆地典型地裂缝的发育特征和成因机理研究，总结了正断型地裂缝的剖面结构特征；进行了地裂缝带土的侧限压缩、三轴压缩和减压三轴试验，总结了不同应力条件下裂缝带土的应力应变特征和变形破坏规律；开展了12组隐伏地裂缝破裂扩展物理模型试验和12组数值模拟分析，总结了地裂缝位错量、裂缝倾角、活动速率、上覆土层厚度、土层性质和地表积水等因素影响对隐伏地裂缝破裂扩展的影响效应，分析了其控制性和敏感性因素；通过模型试验的应力、变形监测和破裂现象观察，确定了不同阶段各破裂的力学行为；结合地裂缝的勘探、破裂扩展试验和数值模拟结果，总结了隐伏地裂缝的破裂扩展演化过程和破坏模式；基于土力学和断裂力学理论，分析了破裂扩展的力学作用机制，解析了不同破裂带宽度。研究结果显示：北京和汾渭盆地构造地裂缝特征典型；地裂缝带土中裂隙的存在对其力学行为影响明显；土性是影响地裂缝破裂扩展的主要因素；地裂缝破裂的力学机制分为剪切、 拉张及拉剪3种,并以拉张为主；地裂缝破裂扩展的演化过程分为隐伏地裂缝开始活动、裂缝端部拉裂、端部反倾裂缝和地表竖向裂缝产生、竖向裂缝向下发展和反倾裂缝延伸变宽、以及竖向裂缝向下与隐伏裂缝贯通和反倾裂缝闭合等5个阶段；地裂缝的破裂扩展分为直线延伸型直接剪切破坏、弧形剪切滑移破坏、直立拉张破坏、反倾拉张破坏和拉剪破坏等5种破坏模式。研究结果对于地裂缝致灾机理认识，地裂缝场地建筑物避让距离设置以及地裂缝灾害综合防治具有重要的理论意义和实际意义。