Rock Mass Characterization for the Underground Surge Pool Cavern – A Case Study, India

Abstract

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.

Engineering geological characteristics of the underground surge pool cavern: a case study, India

“…Integrated approach given by Singh et al [20], Singh and Goel [21] and IS: 15026 [9] is used for the determination of surge pool crown support system capacity. Earlier this approach was used for the construction of underground caverns in the similar type of terrain [10][11][12][13]. The total support pressure (u + p roof ) will be equal to the sum of capacities of support system executed at the crown portion Eq.…”