The Three Gorges Reservoir, one of the largest water conservation system in the world, has been of keen interest to scientists globally since its impoundment. After construction of the dam, there has been a significant increase in seismic activity in the head area of the reservoir. It is generally accepted that earthquakes in this region are predominantly caused by the Jiuwanxi and Xiannvshan faults. This study focused on the stress changes occurring in the research area. A three-dimensional finite element model of the reservoir area was constructed using the geological structure and digital ground elevation data of the reservoir area. The fluid-solid coupling theory was applied to calculate the dynamic spatial changes in pore pressure and Coulomb stress in the faults and surrounding rocks during reservoir impoundment. The findings indicated that the added head pore water pressure at the bottom of the reservoir had a maximum impact range of approximately −2800 m on the surrounding rock, whereas the Xiannvshan and Jiuwanxi faults had a maximum diffusion range of approximately −4300 m. Rock permeability also played a significant role in the water storage process. During the 1 56 m water impoundment stage, owing to rapid water storage activity, stress could not be transmitted to both sides in a timely manner, resulting in the formation of an extreme stress change zone at −4000 m inside the fault. This may have been the reason for the frequent earthquakes during this stage. The 17 5 m cycle water storage stage also exhibited a significant degree of seismicity, potentially attributable to the long-term infiltration of reservoir water and accumulation of stress in the previous stage. The stress in the study area at the four stages are in a process of accumulation-release-accumulation-release.

中文翻译：

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基于流固耦合理论的三峡水库首区应力场分析


三峡水库是世界上最大的水利枢纽之一，自蓄水以来一直引起全球科学家的浓厚兴趣。大坝建成后，水库头区地震活动显着增加。一般认为该地区的地震主要是由九万溪断裂和仙女山断裂引起的。本研究重点关注研究区域内发生的应力变化。利用库区地质结构和数字地面高程数据，构建了库区三维有限元模型。应用流固耦合理论计算储层蓄水过程中断层及围岩孔隙压力和库仑应力的动态空间变化。结果表明，储层底部附加水头孔隙水压力对围岩的最大影响范围约为-2800 m，而仙女山断裂和九湾西断裂的最大扩散范围约为-4300 m。岩石渗透性在储水过程中也发挥着重要作用。 1 56 m蓄水阶段，由于蓄水活动较快，应力无法及时向两侧传递，导致断层内部-4000 m处形成极端应力变化区。这可能是这一阶段地震频发的原因。 17 5 m循环蓄水阶段也表现出明显的地震活动性，可能是由于前阶段水库水的长期渗透和应力积累所致。 研究区应力在四个阶段均处于积累-释放-积累-释放的过程。