深部低孔岩石动力与卸载两扰动互导损伤机制及渗透性响应

The classical theory of damage evolution and permeability response belongs to the category of conventional rock mechanics, which does not match with the cyclic dynamic loading and pressure relieving simultaneous perturbation process on the free surface of deep excavated rock. Due to the cognitive deficiencies of the rock damage mechanism under the double impacts of dynamic loading and pressure relieving, the development of regulation of damage and permeability in disturbed zones of deep rock has been limited. In this project, based on the experimental scientific phenomena of mutual-induced damage subjected to two-disturbance of dynamic loading and pressure found in the previous tests, triaxial test under the double impacts of low-porosity rock will be carried out under the help of a self-developed dynamic disturbance servo triaxial testing system. The macroscopic and mesocopic damage evolution characteristics of low-porosity rock under two-disturbance will be studied using microstructure NRM test, fracture fluorescence observation and mesoscopic simulation. The sensitive analysis of the following factors on damage degree will be made: the unloading velocity of confining pressure, the dynamic disturbance amplitude, the frequency, the duration and the static axial compression ratio. To reveal both the macro and micro mechanical mechanism of two-disturbance damage, the main control element in two-disturbance damage will be observed, and the control interval and threshold will be clarified. Eventually, a coupling expression will be established considering the relationships between the main controlling elements and damage, permeability. The damage constitutive model describing the coupling of two-disturbance and permeability co-evolution will be built. This study is closer to the real disturbance condition of deep rock mass, which can provide a new theory and method for deep rock engineering construction control and the disaster prevention.

经典的岩石损伤演化和渗透性响应理论属于加载岩石力学范畴，与深部岩体经历的开挖循环动力和临空面卸载同步扰动过程严重不符。对动力与卸载两扰动下岩石的损伤机制认知不足，是制约深部围岩损伤和渗透性精细化调控能力的瓶颈。拟借助自主研制的动态扰动伺服三轴试验机，从预试验中显现的两扰动互导损伤特征科学现象出发，开展带AE和渗透率监测的低孔岩石动力与卸载两扰动三轴试验。结合微结构NRM测试、裂隙荧光观察和细观数值模拟，研究低孔岩石两扰动损伤的宏细观演化规律，明确损伤度对卸围压速率、动力扰动幅值、频率、持时及静轴压比等变量的敏感性，解译两扰动损伤的致损主控因素，界定控制区间和阈值。阐释两扰动互导损伤的宏细观力学机制，建立各主控因素与损伤度、渗透率的耦合关系式，最终构建描述两扰动耦合的损伤本构模型和渗透率协同演化模型。本研究更加贴合深部岩体的实际扰动工况，可为深部岩石工程施工控制和灾害预防提供新理论和新方法。

深部工程中岩体处于高应力状态，施工面自身卸荷扰动和远端的外部异源扰动都会改变整个隧洞岩石所处的应力场情况，引发岩石的大变形、大位移，严重时甚至会发生失稳破坏、岩爆等工程灾害。已有的研究通常考虑外部扰动对高应力条件下岩石力学性能的影响。.项目利用动态扰动岩石电液伺服三轴试验系统，对大理岩试样开展单轴高应力状态下的动力扰动试验，不同卸围压路径下的自身卸荷扰动试验，及卸围压与动力扰动联合作用下试验，结果表明：.（1）单轴高应力状态下动力扰动试验发现：①循环动力扰动可诱发处于高应力荷载下岩样损伤进程加快，大大缩短岩样寿命；②扰动变形的衰减段的平均衰减速率，该种方法可有效预测隧洞在受动力扰动的情况下是否会发生岩石快速失稳现象的一种途径；③在循环动力扰动中的最大应变速率与平均弹性模量比较于残余应变可更加准确反应岩样的损伤进程；④动力扰动对岩样损伤一般从岩样中部开始，破坏模式为劈裂破坏，峰值应力比值与扰动幅值越大，破坏越彻底。.（2）不同卸围压路径试验发现：①岩样分级围压路径下破坏比直接卸围压路径下破坏更具突然性；②在偏应力保持一致时，不同初始围压下的岩样失稳时的两个路径下的所对应的失稳时刻围压值几乎相等，说明卸围压的路径并不影响岩样最终失稳的破坏节点；③五个围压水平下卸荷破坏的岩样均为具有单一的斜向主破裂面，直接卸荷下虽初始围压不同但剪切角却相对不变，而在分级卸荷下随着初始围压的增大，剪切角也逐渐变大。.（3）卸围压与动力扰动联合作用试验发现：①加载扰动未破坏岩样的平均衰减速率要比卸荷与扰动联合作用下未破坏岩样的平均衰减速率小一个数量级，在突然性破坏岩样中，只有第三阶段的加速非线性变形段。；②循环应变速率对于卸荷量的响应并不大，对于扰动阶段的扰动幅值则更加敏感；③破坏岩样中部向四周鼓胀明显，破坏模式为剪切破坏，延性大大加强。