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松动区是控制地下洞室围岩变形及失稳的重要因素。以锦屏一级水电站为例,结合声波测试及多点位移计监测成果,对高地应力和低强度应力比条件下大型地下厂房围岩松动区的分布及变化特征进行分析,并采用BP网络和遗传算法对围岩参数进行反演。研究表明,声波测试的围岩松弛深度与多点位移计监测得到的围岩主要变形深度具有一致性,围岩松弛深度变化趋势与岩壁位移变化也存在对应关系,两者结合可以对围岩松动区的变化规律进行连续的分析。高地应力和低强度应力比条件下的松动区深度远大于一般应力条件,由于围岩应力状态调整、岩体破坏所导致的卸荷松弛成为围岩松弛的主要因素。开挖过程中,由于围岩应力状态的逐步调整,导致围岩的破坏和松弛的渐进发展,其中松弛深度在水平向的扩展较为明显。反演得到的松动区岩体变形模量及黏聚力较未松动岩体有明显降低,而摩擦角降低较少。因此,对松动区岩体进行灌浆加固,将有助于提高松动区岩体的变形模量和粘聚力,从而增强围岩的稳定性。
Loose zone is to control the underground cavern surrounding rock deformation and instability of the important factors. Taking Jinping Hydropower Station as an example, this paper analyzes the distribution and variation characteristics of loosening zone in surrounding rock of large-scale underground powerhouse under high ground stress and low strength stress ratio based on the results of sound wave test and multi-point displacement meter monitoring. By using BP network and Genetic algorithm inversion of surrounding rock parameters. The results show that the relaxation depth of surrounding rock by acoustic wave test is consistent with the main deformation depth of surrounding rock measured by multi-point displacement meter, and the trend of relaxation depth of surrounding rock is also corresponding to the displacement of rock wall. Loose zone changes in the law of continuous analysis. The depth of loosening zone under high-stress and low-intensity stress conditions is much larger than the general stress conditions. Due to the stress state adjustment of surrounding rock, the unloading relaxation caused by the failure of rock mass becomes the main factor of the surrounding rock relaxation. During excavation, due to the gradual adjustment of stress state of surrounding rock, the destruction of surrounding rock and the gradual development of relaxation are caused. The relaxation depth is more obvious in the horizontal direction. The deformation modulus and cohesion of the loose rock mass obtained in the inversion are obviously lower than those of the unsteady rock mass, while the friction angle decreases less. Therefore, grouting and reinforcement of loose rock mass will help to improve the deformation modulus and cohesion of rock mass in loosening area, and thus enhance the stability of surrounding rock.