爆破循环开挖下深部巷道围岩层裂结构形成机理和稳定性研究

Under complicated geologic mechanical environments, the failure and instability of surrounding rocks of deep roadway induced by blasting excavation pose enormous threat to resource exploitation in deep mining engineering. In the project, the spall and stability of surrounding rocks in deep roadway under blasting excavation are observed. After a serious of laboratory and model tests, free surface effect of explosion stress wave through high stress and rock mass with fracture are studied, including the cumulative damage effect of surrounding rocks in roadway. Based on theories of damage and fracture mechanics, the dynamic cumulative damage constitutive model is established. Based on the theories of energy and catastrophe, the instability model of spallation structure is finished. The spallation and stability mechanism under blasting rounds digging are revealed via numerical simulation, and verified through field test. So as to offer an important theoretical basis for the judgments of stability and support designs of deep roadway.

深部巷道处于复杂的地质力学环境下，爆破开挖诱发围岩破裂失稳给深部资源开采造成巨大威胁。本项目以爆破开挖下深部巷道围岩的层裂化和稳定性为研究对象，采用室内试验和模型试验，研究爆炸循环应力波在高应力裂隙岩石中的自由面效应、巷道围岩损伤累积效应；基于损伤断裂力学理论，建立裂隙岩体的动态累积损伤力学模型，基于能量理论和突变理论，建立层裂结构失稳模型；通过数值模拟，揭示爆破循环开挖下围岩层裂结构的演化机理和稳定性机制，现场测试进行验证，为深部巷道的稳定性判定和支护设计提供重要的理论支撑。

本项目围绕深部爆破开挖卸荷引起的围岩层裂结构进行了相关研究，建立了基于能量耗散和声发射的岩石损伤本构模型、研究了岩石材料应变局部化剪切带的形成，以及深部圆形巷道开挖卸荷的围岩力学特征及破坏机理，自行研制了深部巷道开挖卸荷效应的模拟装置，进行了深部巷道循环开挖的卸荷试验。结果表明：建立在能量耗散和声发射基础上的岩石损伤本构模型可以较好地反映岩石在单轴压缩下的损伤演化规律，材料参数分别影响应力强化、软化和整体应力-应变曲线；光滑边界应变局部化剪切带形成于试件上下端面，摩擦边界形成于试件中部区域，且摩擦边界时试件的峰值强度高于光滑边界，峰值强度后的软化阶段陡峭于光滑边界，这一研究成果有助于加深理解岩石破坏过程；深部开挖卸荷下围岩力学特征主要表现为最小主应力卸荷、最大主应力集中，而主应力差的瞬间增大，诱发开挖面内裂隙扩展、贯通，形成由强及弱连续分布的破坏区，构成二次支护前维系围岩稳定的支撑结构，分析结果对深入研究高地应下巷道开挖的破坏机制具有重要意义；循环动态开挖仅引起近处岩体显著卸荷，且卸荷指标呈非线性变化；在侧压系数K=1.2情况下，开挖卸荷导致围岩的破坏主要集中在两侧巷帮，而损伤随径距增加逐渐衰减，实验结果表明了深部开挖卸荷是诱发巷道围岩产生层裂结构的主要因素。