Abstract We present results from an international model comparison study involving a series of controlled fault activation experiments in Opalinus Clay at the Mont Terri Laboratory, Switzerland. The fault activation experiments were conducted in situ by water injection at variable pressure from boreholes targeting different parts of the Main Fault crossing several tunnels and galleries of the Mont Terri Laboratory. The model simulations focused on (1) an experiment activating a discontinuity (fracture or minor fault) within the damage zone of the main fault, and (2) an experiment activating discontinuities close to the core of the Main Fault. The experimental data consist of coupled hydraulic and mechanical responses monitored at an injection borehole and a monitoring borehole located a few meters away. After overcoming several modeling issues along with necessary model developments, a reasonably good agreement was achieved between the modeling results and the field observations. The fault activation experiments displayed an abrupt flow rate increase associated with a sudden fracture opening and rupture propagation after the injection pressure reached above the estimated normal stress on the fracture. This was followed by an abrupt flow rate decrease, indicating hydraulic closing, once the injection pressure decreases to an estimated 1–2 MPa below the stress normal to the opened fracture. The models were able to capture this abrupt hydromechanical behavior, including an observed dominant opening behavior along with the rupture propagation, while the spatial extent of the shear rupture and the quantity of peak injection flow were the most challenging to predict.

中文翻译：

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Mont Terri实验室泥质粘土岩受控断层激活实验的国际模型比较研究

摘要 我们介绍了一项国际模型比较研究的结果，该研究涉及瑞士 Mont Terri 实验室的 Opalinus Clay 中的一系列受控断层激活实验。断层激活实验是通过从针对主断层不同部分的钻孔中以可变压力注入水的方式进行的，这些钻孔穿过 Mont Terri 实验室的几个隧道和画廊。模型模拟的重点是（1）激活主断层破坏带内的不连续性（断裂或小断层）的实验，以及（2）激活主断层核心附近的不连续性的实验。实验数据包括在注入钻孔和位于几米外的监测钻孔处监测的耦合水力和机械响应。在克服了几个建模问题以及必要的模型开发之后，建模结果和现场观测之间取得了相当好的一致性。断层激活实验显示，在注入压力达到估计的裂缝正应力以上后，与突然的裂缝打开和破裂扩展相关的流量突然增加。随后是流速突然降低，表明一旦注入压力降低到低于打开的裂缝的法向应力估计 1-2 MPa，则表明液压关闭。这些模型能够捕捉到这种突然的流体力学行为，包括观察到的主要打开行为以及破裂传播，