Visualization and early warning analysis of damage degree of surrounding rock mass in underground powerhouse

Based on the underground powerhouse of Shuangjiangkou hydropower station, Octree theory is adopted to define the indices of the microseismic (MS) spatial aggregation degree and the deviation values of MS count and energy. The relationship between the MS multiple parameters and surrounding rock mass instability is established from three aspects: time, space, and strength. Supplemented by the center frequency of the signal evolution characteristics, A fuzzy comprehensive evaluation model and the evolution trend of the MS event center frequency are constructed to quantitatively describe the early warning state of the surrounding rock mass instability. The results show that the multilevel tree structure and voxels generated based on the Octree theory fit relatively well with the set of MS points in three-dimensional space. The fuzzy comprehensive evaluation model based on MS spatial aggregation and MS count and energy deviation values enables three-dimensional visualization of the potential damage area and damage extent of the surrounding rock mass. The warning time and potential damage zone quantified are highly consistent with the characteristics of MS precursors, with wide recognition and field investigation results, which fully validate the rationality and applicability of the proposed method. These findings can provide references for the early warning of surrounding rock mass instability in similar underground engineering.