考虑时间尺度的岩石变形记忆效应形成机理及试验研究

Knowledge of magnitudes and orientation of the in situ stress is critical in both the geologic science and rock engineering. Auctully the measurement of the in situ stress is not an easy task. A significant amount of experimental works done by researchers from many countries show that the in situ stress can be determined by the rock deformation memory effect (DME). It has natural advantages over traditional methods. However, The lack of research on the mechanism and theoretical model of the time effects in the DME prevents the improvements of the DME method. .Base on the mechaism that frictional sliding over the microcrack interfaces and grain boundaries controls the DME, a new mechanism for the time effects is proposed in the propasl: the creep of the viscous medium and the potentional ennergy translation between the viscous medium and elastic matrix controls the time effects. Theoretical model of the DME with time effects will be developed by the combination of elastic elements, St. Venant bodies and dashpots. Combined with the theoretical model, physical experiments under different loading regimes will be employed to reveal the law of the DME and its time effects. To give an answer to the influences of the holing time, the delay time, the repeated loading times on the DME and its times, the loading regimes will be specially designed with different holding time, delay time and repeated loading times. The permanent memory effect, the long-term memory effect, the short-term memory effect and memory fading with the delay time will also be explained in the research. Finally, the differences and characteristics in common between the artificial memory effect and the in situ stress memory effect will also be explored. .The expected results of this research will provide mechaical foundation and experimental basis for the use and improvments of the DME method in determining the in situ stress.

地应力的测量是各类岩石工程后续工作的基础，也是难点之一。岩石变形记忆效应为简便、准确测量地应力，提供了全新思路，国际上一系列研究应用成果展示了其极大潜力。岩石变形记忆效应及在时间尺度上特征的形成机理的研究不足，成为制约这种方法完善改进的核心问题。①提出岩石内部微裂纹及颗粒接触面间黏性介质的流变特性及其与弹性基质的势能“转移”，是产生时间尺度上诸多特征的机理，并将基于此采用基本三元件构建考虑时间尺度的理论模型；②将结合理论模型及不同时间尺度下物理试验，揭示时间特征的内在运行机制及外在表现规律；③结合理论及试验，研究地应力记忆效应失忆性及与人工记忆效应异同点。预期成果对放置时间、加载保持时间、加载重复次数的影响，永久、长期、短期记忆、失忆性等现象，测地应力前岩芯暴露时间、人工记忆效应成果运用于地应力记忆效应研究的条件等诸多问题进行解答，为采用变形记忆效应测量地应力提供力学基础及试验依据。

初始地应力是岩石工程变形破坏的根本作用力，其大小和方向信息的准确测量是岩石工程分析决策的基础，但是，也一直是工程界的难点问题之一，特别对于我国深地发展战略来讲。岩石变形记忆效应为简便、准确测量地应力，提供了全新思路，目前国内外大量研究与应用成果展示了其极大前景。岩石DME及其时效特征形成机理的研究不足，成为制约这种方法完善改进提高的瓶颈。本课题1）开展了不同材料的变形记忆效应物理试验，与岩石DME进行对比。同时对于岩石DME的特征，开展了包含岩石DME基本特征试验研究，循环加载对岩石DME特征影响规律试验研究，不同应力峰值组合下的岩石DME记忆信息试验研究，考虑时间尺度的岩石记忆信息失忆特征试验，等应力蠕变加载下岩石DME特征试验研究等。（2）针对岩石DME及时间特征的形成机理，基于申请人前期提出的岩石内部微裂纹及颗粒接触面的摩擦滑动机理的基础上，提出岩石微裂纹及颗粒接面间黏性介质的流变特性及及应力作用下黏性介质与弹性基质的势能“转移”，是造成DME诸多时间特征的机理。在此基础上上，采用基本三元件构建考虑时间尺度的记忆单元，并且借助无量纲分析法及正态、均匀分布对参数进行了分析，并模拟岩石内部多裂纹及颗粒接触面的力学行为从而描述岩石的变形记忆效应。（3）基于多记忆单元理论模型，得到岩石DME特征，与物理试验结合，指出地应力记忆效应失忆性及与人工记忆效应异同点。通过物理试验及理论模型中的时间特征对比研究，得到了时间、循环加载对DME的影响，揭示DME时间特征机制，解答永久记忆、长期记忆、短期记忆的形成，指出地应力记忆效应的时间特征研究及与人工记忆效应的异同点。研究成果揭示了岩石变形记忆效应的形成机理，回答了岩石内部结构何种物理现象造成了岩石变形记忆效应及其特征，并且建立了可以描述这种力学行为理论模型，为DME的研究奠定了基础。对于地应力记忆效应的解答为DME在地应力测量领域的应用提供了实验及理论基础。