地下储油洞库一般选址在坚硬的结晶岩地区,洞室围岩稳定问题主要表现为局部的块体失稳。块体理论采用几何拓扑学方法分析地质结构面相互切割形成的块体及其稳定问题,是分析地下洞室围岩稳定性的理想工具。依托某在建地下水封洞库工程,总结形成了工程岩体开挖现场块体预测分析流程。首先,根据前期勘察和主洞室顶层开挖获得的地质素描资料,分析总结主洞室结构面发育规律;然后,对结构面进行组合,利用全空间赤平投影法,判别各组合在主洞室中下层边墙可能出现的可动块体和关键块体;随后,采用最大块体形态分析方法,对关键块体进行几何形态分析,剔除“浅埋型”和“尖长型”这两种非支护关键块体,获得需支护关键块体;最后,对需支护的“端正型”关键块体提出支护建议。研究成果为洞室围岩支护设计提供了理论分析依据,在岩石地下工程建设中具有重要的推广价值。

[Objective] Underground oil storage caverns are typically located in areas with hard crystalline rock, where the stability of surrounding rock mainly manifests as localized block instability. Traditional rock mass classification methods focus solely on analyzing and evaluating the overall stability of the surrounding rock, often neglecting the problem of block instability caused by unfavorable combinations of structural planes. [Methods] Block theory, utilizing geometric topological analysis to evaluate rock blocks formed by intersecting structural planes and their stability characteristics, serves as an effective approach for assessing the stability of underground caverns. Building on this block theory, this study utilized the whole-space stereographic projection method to identify removable blocks formed by the combinatorial intersection of various structural planes. The residual sliding force of these removable blocks was then used to determine whether they were key blocks requiring support. Subsequently, key blocks underwent maximum block morphology analysis to eliminate non-engineering-support blocks. Finally, positional block analysis was performed on blocks requiring support. [Results] This study developed a comprehensive flowchart for on-site block prediction analysis during engineering rock mass excavation. The specific analysis process was as follows. First, the development patterns of structural planes in the main cavern were analyzed and summarized based on geological mapping data obtained from preliminary surveys and the excavation of the main cavern’s top layer. Next, structural planes were combined, and the whole-space stereographic projection method was employed to identify potential removable blocks and key blocks that may form on the middle and lower sidewalls of the main cavern for each combination. Then, the geometric morphology of these key blocks was analyzed using their maximum block shape. Finally, blocks requiring support were identified based on their maximum block morphology, and corresponding support schemes were proposed. [Conclusion] The main conclusions are as follows: (1) through full-space stereographic projection analysis of various combinations of structural planes, the removable blocks and key blocks formed by these combinations on the left and right sidewalls were identified. (2) Based on the maximum block morphology of each key block, “shallow-buried” and “slender” types of non-support key blocks were eliminated, leaving only the “compact” type of blocks requiring support. (3) Support schemes were proposed based on the actual morphology of the identified “compact” blocks. The findings provide a theoretical foundation for the support design of cavern surrounding rock and hold significant value for broader applicability in rock underground engineering construction.