Excavation of Large Underground Surge Pool Benching and Delivery Mains (Vertical Shafts) with the Alimak Raise Climber Method - A Case Study

Excavations of large underground caverns and delivery mains (vertical shafts) are always time taking and expensive, when conventional methods are used for mucking during different levels of benching and shaft sinking. For completing the excavation of surge pool benching and delivery mains (vertical shafts) within time and cost-effective, glory holes technique were applied for mucking purpose for different levels of benching for surge pool and delivery mains. A Surge pool 375 m (L) x 25 m (W) x 67.6 m (H) and seven numbers of delivery mains of 100 m (H) x 6.0 m (W) were constructed in the Telangana State of India for lift irrigation purpose. To complete the excavation of these structures Alimak Raise Climber method was adopted to excavate initial glory holes for mucking. This method best suited to good and very good rock conditions. On the basis of engineering geological mapping of rock mass of heading, bench foundation and bore holes data good to very good rock mass was anticipated at different reduce levels in the surge pool benches and delivery mains locations. A 2.5 diameter vertical glory hole was dug up from surge pool bottom to bench 3 levels for 21 m. Other glory holes were dug up from bottom of the delivery mains to ground level for more than 100 m. Rock type exposed is mainly grey and pinkish granite belonging to Peninsular Gneissic Complex of Archaean age. Prediction of rock mass for different reduce levels were challenging and if not anticipate properly it would have risky during the operation of Alimak Raise Climber. In this case, rock mass was met as predicted. This method will be helpful for mucking of the similar large underground caverns and delivery mains (vertical shafts) if rock mass can be predicted properly.