Characterization of the Subsurface Fracture Network by Means of Crystal Fracture Mechanics and Crystal Stress Study

通过晶体断裂力学和晶体应力研究表征地下断裂网络

• 批准号: 05044197
• 负责人: TAKAHASHI Hideaki
• 金额: --
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Overseas Scientific Survey.
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 无数据
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05044197/
• 关键词: Fracture; Fractal; Subsurface Fractures; Numerical Simulation; Crustal Stress; Permeability; Connectivity; Rock

The observed fractal nature of both fault length distributions and earthquake magnitude-frequency distribution suggests that there may be a relationship between the structure of active fault systems and the resulting seismicity. Here, we present the first experimental evidence for a correlation between the fractal dimension of fracture length distribution D and acoustic emission (AE) b-value based on a series of tensile fracture mechanics tests on crystalline rock, carried out in different environmental conditions, both air-dry and water-saturated at ambient temperature and pressure. The constant stress intensity, K_I, and quantitative analyses of the resulting fracture patterns were carried out on the same specimens. It is found that AE b-values, ranging from 1.0 to 2.3, correlate negatively with normalized stress intensity K_I/K_<IC>, where K_<IC> is the fracture toughness of the specimen. The fractal dimension of fracture length distribution D, ranges from 1.0 to 1.7. Fluid presence has a first-order influence on both the AE and structure produced in these experiments. For experiments at low stress intensity or high fluid content, the activation of the stress corrosion mechanism for K_I < K_<IC> leads to a greater relative proportion both of small cracks and of low amplitude acoustic emissions, reflected in higher values of D and b. The fractal dimension D is found to correlate positively with the AE b-value.

断层长度分布和地震幅度频率分布的观察到的分形性质表明，活动断层系统的结构与所得的地震性之间可能存在关系。在这里，我们提供了第一个实验证据，证明了基于在不同环境条件下在不同环境条件下进行的一系列拉伸裂缝力学测试，基于一系列抗晶岩的拉伸断裂力学测试，裂缝长度分布D与声发射（AE）B值之间存在相关性（AE）B值。在相同的标本上对所得断裂模式的恒定应力强度，K_I和定量分析进行了定量分析。发现AE B值范围为1.0至2.3，与归一化的应力强度K_I/K_ <ic>负相关，其中K_ <ic>是样品的断裂韧性。断裂长度分布D的分形维度为1.0至1.7。流体的存在对这些实验中产生的AE和结构都有一阶影响。对于低应力强度或高流体含量的实验，K_I <k_ <ic>的应力腐蚀机制的激活导致相对比例较大，而相对比例的小裂纹和低振幅声学排放均反映在较高的D和B值中。发现分形维度D与AE B值正相关。