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地应力信息储存于开挖后的岩石中,变形率变化法(DRA)是基于岩石变形记忆效应测量地应力的方法,正确的机制是认识变形记忆效应与推广、改进DRA法的基础。传统推测的机制并不能解释低应力区存在变形记忆效应及失忆性等现象。首先进行火山沉积岩试样的物理试验,证明低应力区仍然存在变形记忆效应,记忆信息可同时采用侧向应变及轴向应变测量,两者精度一致。提出在低应力区,岩石变形记忆效应机制为微裂纹接触面及颗粒接触面的摩擦滑动。基于此机制,采用弹性元件、黏性元件和圣维南体构建相应的轴对称理论基本单元模型及多接触面理论模型。进行不同放置时间下的单轴循环压缩试验。结果表明,由轴对称理论模型可以得到低应力区岩石变形记忆效应、侧向DRA曲线与轴向DRA曲线准确度一致且在记忆信息处向上弯曲等、并对失忆性现象进行了初探。理论模型与物理试验结果一致,由此证明微裂纹接触面及颗粒接触面的摩擦滑动可以得到低应力区岩石变形记忆效应。同时,理论模型及物理试验结果为提高DRA法的测量准确度提供了依据。
The ground stress information is stored in the rock after excavation. The method of change of deformation (DRA) is a method of measuring geostress based on the deformation effect of rock deformation. The correct mechanism is to understand the effect of deformation memory and its promotion, and to improve the foundation of DRA method. The traditional speculation mechanism does not explain the existence of deformation memory effect and amnesia in low-stress areas. First of all, physical tests of volcanic sedimentary rock samples are carried out to prove that there is still deformation memory effect in the low-stress region. The memory information can be measured by lateral strain and axial strain simultaneously, and the accuracy of the two is consistent. It is proposed that in the low-stress zone, the memory effect mechanism of rock deformation is the frictional sliding between the micro-crack contact surface and the particle contact surface. Based on this mechanism, the basic unit model of axisymmetric theory and the theoretical model of multi-contact surface are constructed by elastic elements, viscous elements and Sheng-Venan body. Uniaxial cyclic compression tests were performed at different placement times. The results show that the rock deformation memory effect of low stress zone can be obtained from the theoretical model of axisymmetry. The lateral DRA curve is consistent with the accuracy of axial DRA curve and curved upward at the memory information, and the phenomenon of amnesia is also discussed. The theoretical model is in good agreement with the physical experiment, which proves that the frictional sliding of the interface between the microcracks and the particle can obtain the deformation and memory effect of rock in the low-stress region. At the same time, theoretical models and physical test results provide the basis for improving the measurement accuracy of DRA method.