高水平应力区巷道开挖卸荷破裂演化规律与围岩结构性蠕变机理研究

The complex instability characteristics of the deep excavation roadway are difficult to clarify, such as: the serious deformation fracture of rock strata, the reduced bearing capacity of surrounding rock and the occurrence of structural creep. However, some complicated theoretical problems on fracture evolution law of excavation unloading roadway under high horizontal stress and structural creep mechanism of surrounding rock remain to be resolved. The project conducts the rock unloading mechanical tests with and without confining pressure, obtains the main rupture points which are the characterization parameters of rock acoustic emission threshold in rock yield phase, grasps the space-time distribution laws of main rupture points and its main fracture surface under the influence of high confining pressure and different unloading path, and fits relation curve between the above space-time distribution laws and the distribution of yield shear stress which is the equivalent shear stress threshold. Based on field measurement and numerical simulation, we propose the theoretical mechanical model of the shear bearing structure of surrounding rock with considering the shear yield stress. At the same time, we grasp the formation and evolution law of shear bearing structure under high horizontal stress, and reveal its space-time correlationship with the occurrence and development of surrounding rock microfractures. In physical model test, we analysis of the stability of shear bearing structure and the fracture evolution law of surrounding rock under the influence of high confining pressure, unloading, etc. In the theoretical calculation with considering high horizontal stress, the shear strain is introduced to deduce the creep equation of the outside boundary of shear bearing structure, the creep characteristic parameters of the shear bearing structure and its dynamic correlationship with the visco-elastic plastic solution of surrounding rock are described by mathematical method. The research provides the theoretical basis for clarifying fracture evolution and structural creep mechanism of deep roadway.

目前很难清楚阐明深部开挖巷道复杂失稳特征如：岩层变形破碎严重、围岩承载能力降低以及结构性蠕变现象发生，针对高水平应力区巷道开挖卸荷破裂演化规律与围岩结构性蠕变机理等深层次理论问题亟待解决。项目采用有、无围压下卸荷试验，确定岩石屈服阶段声发射阈值表征的主破裂点，掌握高围压、卸荷路径影响下岩石主破裂点及其所形成的主破裂面时空分布规律，并拟合其与屈服剪应力分布之间关系曲线。由现场实测结合数值模拟，考虑屈服剪应力影响建立围岩抗剪承载结构的理论力学模型，研究抗剪承载结构的形成和演化规律，并揭示其与围岩微裂隙产生、发展之间的时空关系。开展围压、卸荷等影响下物理模型试验，研究巷道破裂演化规律与围岩抗剪承载结构稳定性。在高水平应力理论计算中，引入剪应变建立围岩抗剪承载结构边界线蠕变方程，数学描述抗剪承载结构的蠕变参数及其与围岩粘弹塑性解之间动态关系。以期为阐明深部巷道破裂演化和结构性蠕变机理提供理论依据。

项目针对深部巷道复杂失稳特征，即岩层变形破碎严重、围岩承载能力降低以及结构性蠕变等深层次理论问题亟待解决。采用了有、无围压下卸荷试验，确定了岩石屈服阶段声发射阈值表征的主破裂点，掌握了高围压、卸荷路径影响下岩石主破裂点及其所形成的主破裂面时空分布规律，并拟合其与屈服剪应力分布之间关系曲线。考虑了屈服剪应力影响建立了围岩抗剪承载结构的理论力学模型，研究得出了围岩抗剪承载结构的形成和演化规律，并揭示了其与围岩微裂隙产生、发展之间的时空关系。最后，通过引入剪应变建立了围岩抗剪承载结构边界线蠕变方程，数学描述了围岩抗剪承载结构的蠕变参数及其与围岩粘弹塑性解之间动态关系。项目研究表明：（1）有、无围压试验结果：无围压下循环加卸荷相较于分级加卸荷，岩石内部破裂更明显；卸荷过程声发射事件点处于振荡期，集中应力区域声发射事件激增明显，不同应力路径下声发射事件点的振荡期、激增程度均不同；有围压下卸荷过程声发射事件点处于振荡期，屈服应力区域声发射事件激增明显，围压施加特别是高围压施加后对岩块的细观破裂发育影响较大；同时，试件尺度越大声发射能量值受高应力影响越明显，但声发射事件数呈现相反趋势，即尺寸越大岩石破裂后碎块体积大；通过编制Matlab内置软件并依据声发射能量值，区分不同事件数的大小，重新勾勒岩石声发射破裂信号。（2）巷道破裂演化规律：在外部加载的持续作用下，随着巷道开挖向前推进，围岩内部出现裂纹逐渐发育、扩展与相邻次生裂纹搭接贯通，宏观上体现为相似模型体积扩容；（3）抗剪结构承载机理及蠕变规律：由围岩松动圈演化规律和围岩“剪切失稳区+抗剪承载区”宏观结构的测试结果可知，围岩剪切失稳区分布和变化趋势与围岩松动圈中破碎带分布和变化趋势较吻合，表明该区域已发生失稳;围岩抗剪承载区分布规律与松动圈中塑性带分布范围相似，表明该承载区易发生剪切滑移失稳。（4）围岩结构性蠕变数学描述：巷道开挖破坏后，围岩弹塑性变形完全释放，由于应力场和位移场发生变化，导致承载区的形成和发展。而此时，各承载区内围岩强度已发生变化，从而导致沿巷道径向各点处的蠕变发展过程不一致，其中瞬时蠕变导致各承载区瞬间扩大。而加速蠕变的时间不一致也会导致承载区进一步扩大，随着进入蠕变稳定期，各承载区范围不再发生变化。