Underground surge pool cavern for the storage and lifting of water is being constructed in the part of Telangana State of India. For better rock mass characterization and support design, 3D engineering geological mapping was carried for the heading portion of the surge pool. 3D geologic mapping of heading portion is very important for large underground cavern to know about the cavern behavior during benching down. The direction of the longest axis of the cavern was finalized based on the in-situ hydrofracturing testing inside the deep borehole. The assessment of tunnel quality index ‘Q’ for the exposed granitic rock mass was done based on the information available of the rock joints and their nature, 3D geological mapping and in-situ stress measurement. Roof support and wall support pressure was estimatedbased on Q-values, and in this case applicable for the non-squeezing ground condition. For structural stability of crown and walls, rock support arrangement was recommended based on NMT technology and geological conditions of site, which includes steel fibre reinforced shotcrete, grouting, rock bolt and drainage hole provisions. The capacity of support system is determined to evaluate the efficacy of the proposed support system.

中文翻译：

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地下涌水池洞穴的岩体特征——印度案例研究

用于储存和提升水的地下调压池洞穴正在印度特伦甘纳邦的部分地区建造。为了更好地进行岩体表征和支护设计，对缓冲池的水头部分进行了 3D 工程地质填图。掘进部分的 3D 地质填图对于大型地下溶洞了解下沉过程中的溶洞行为非常重要。洞室最长轴线方向根据深孔内原位水力压裂试验确定。基于岩石节理及其性质、3D 地质图和现场应力测量的可用信息，对暴露的花岗岩岩体的隧道质量指标“Q”进行了评估。屋顶支撑和墙壁支撑压力是根据 Q 值估算的，在这种情况下适用于非挤压地面条件。为保证冠墙的结构稳定性，建议根据NMT技术和场地地质条件进行岩体支护，包括钢纤维喷射混凝土、灌浆、锚杆和排水孔规定。确定支持系统的能力以评估所提议的支持系统的功效。