等间距破裂层状岩体开挖扰动下的失稳机理及其结构效应研究

Equally spaced fractures based on statistics in layered rock are important phenomena for sedimentary rock and also different for excavation. With different fracture spacing, the rock mass exhibits different structure characteristics that the rock mass changes from bedding architecture to blocky structure. Therefore, the collapse mechanisms for equally fractured layer-rock are very complex. As the engineering background, the collapse mechanism of the layered rock mass under excavation and the structure effect of rock mass are investigated. The stratigraphic structure and fracture network are obtained by the digital borehole camera technique. Then the relationship between the fracture spacing index (FSI) and surface appearance of fractures and mechanics parameters are explored by laboratory tests. The white digital speckle correlation methods are adopted to investigate the fracture evolution in layer rock. The structure effect for the layered rock is also analyzed and then the model for fracture evolution path considering the structure effect in layered rock is developed. The model tests are carried out to study the collapse modes of the layered rock under excavation. The structure effect on collapse characteristics is analyzed. And the collapse mechanisms for equally fractured layer-rock mass are then deeply explored. The results from this project provide theoretical significance and practical value for deformation and stability control of roadways, tunnels and caverns in layered rock.

层状岩体在统计上的等间距破裂是一种重要的地学现象，也是地下工程施工的难点。随裂隙间距减小，层状岩体呈现出不同的结构特征，即从层理结构向块体结构转变，其失稳机理异常复杂。项目以此为背景，研究等间距破裂层状岩体在开挖扰动下的失稳机理以及岩体结构特征不同所产生的结构效应。通过现场数字钻孔摄像技术，结合室内试验探明等间距破裂层状岩体的结构特征与裂隙几何形貌特征之间的关系。利用白光数字散斑相关方法，从细观角度揭示等间距裂隙在层状岩体中扩展演化特性以及裂隙在层状岩体中扩展的结构效应；构建反映岩体结构效应的等间距裂隙扩展力学模型。通过岩体开挖模型试验，从宏观角度研究等间距破裂层状岩体破坏特征以及扰动失稳结构效应；揭示等间距破裂层状岩体开挖扰动下的失稳机理；提出考虑岩体结构效应的失稳判据。项目成果对解决层状岩体中的巷道和地下硐室等工程的变形和稳定性问题有重要的理论意义和实用价值。

等间距破裂层状岩体是岩石工程常见的复杂介质。裂隙间距不同，层状岩体呈现出不同的结构特征，即从层理结构向块体结构变化，其失稳机理异常复杂。项目拟以此为背景，对等间距破裂层状岩体在开挖扰动下的失稳机理及岩体结构特征变化所引发的结构效应展开研究。通过现场测试、室内试验、数值模拟和理论分析，揭示了等间距裂隙的形成规律、其分布特征及其宏细观结构特征,并基本三线式粘结滑移模型推导了等间距破裂裂隙间距的理论计算公式，揭示岩层厚度、界面强度、横截面面积等因素对裂隙分布规律的影响机制。分析了裂隙在层状岩体中闭合、滑移、扩展及相互作用的过程；分析层状岩体结构特征的变化对裂隙扩展特性的影响；基于界面断裂理论，分析了界面裂隙的扩展演变规律；构建反映岩体结构效应的等间距破裂岩体中裂隙扩展力学模型。基于地质模型试验，研究等间距破裂岩体开挖扰动下破坏过程、破坏模式、破坏范围等特征分析岩层岩性组构、岩层倾角及围压对层状围岩破坏特征的影响；研究层状岩体从层理结构向块体结构变化对其破裂特征的影响；揭示等间距破裂层状岩体开挖条件下的失稳机理；提出考虑岩体结构效应的失稳判据。项目成果为层状岩体的稳定性控制供有效的理论依据。