# Rock Mass Structure Classification of Caves Based on the 3D Rock Block Index
## 7 Conclusions  
1. Taking the rock mass of the long exploratory cave CPD1 in the water transmission system of the Qingtian pumped storage power station in Zhejiang province as the research object, the rock mass of the flat cave is statistically homogeneous, and the probability model of joint parameters in each homogeneous zone is obtained.
2. According to the probabilistic model of joint parameters, the Monte Carlo method was used to develop stochastic simulations of joints, and the 3D network model of joints in the rock mass of a flat cave in each segment was established. Through the comparison of graphs and data, it is concluded that the 3D joint network simulation based on statistics and probability can realize the visualization of rock mass structure, effectively improve the precision of the 3D joint network simulation, and more accurately reflect the structural characteristics of actual rock mass.
3. Based on the 3D joint network model, virtual survey lines are arranged on the front, side, and top surfaces of the model to represent the borehole, and the RBI values of 108 virtual survey lines on the three orthogonal planes are counted. Using the concept of 3D rock block index, the fine classification of the flat cave rock mass structure is conducted. The results of the structural classification of flat cave rock mass based on the 3D rock block index show that the rock mass structure of the long-tunnel CPD1 is classified as that which is from overall structure to blocky structure, corresponding tothe integrity of rock mass being complete to relatively complete. The classification results are consistent with the evaluation results of horizontal tunnel seismic wave geophysical exploration.
* Compared with traditional rock mass classification methods and classification indexes, the 3D rock block index can more accurately reflect the structural characteristics of rock mass. It can be used as a quantitative index to directly reflect the anisotropy of rock mass structure in three-dimensional space. Therefore, it is reasonable and feasible to use the 3D rock mass index as a quantitative evaluation index to analyze the type of rock structure, and it is helpful and meaningful in the classification of underground engineering rock structures.  
Conceptualization, J.D.; methodology, J.D.; software, J.D.; validation, J.D.; formal analysis, J.D.; investigation, J.D.; resources, Q.C.; data curation, J.D.; writing--original draft preparation, J.D.; writing--review and editing, J.D.; visualization, K.X.; supervision, J.D.; project administration, J.D.; funding acquisition, G.Y. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the key research and development project of Henan Province (No. 221111321500).  
The source of the data in this article has been reflected in the text.  
All authors contributed to the study conception and design. No conflicts of interest exist in this manuscript, and the manuscript has been approved by all authors for publication. I would like to declare on behalf of my co-authors that the work described was original research that has not been published previously, and not under consideration for publication elsewhere, in whole or in part. All authors read and approved the manuscript.