Abstract: Currently, dewatering scheme is typically designed using the method of theoretical calculation and numerical simulation. The designed scheme, however, is far from the optimum, since the total pumping rate can be further optimized with engineering safety ensured. Based on the dewatering in the 2nd confined aquifer of a cut and cover tunnel belonging to the north part of Jiangyin-Jingjiang Yangtze River tunnel project, dewatering optimization is conducted combining the methods of linear programming (LP) and numerical simulation. In advance, the hydraulic conductivity is adjusted by simulating the pumping test. Then, the parameters required in the LP model are obtained with numerical simulation. The pumping wells with optimal locations and the corresponding pumping rates are further determined, and the results are compared with the ones in actual construction. It is found that more number of pumping wells and more rational well location usually result in lower total pumping rate and drawdown. For the cut and cover tunnel with gradually changing excavation depths along the tunnel, dewatering in the deepest excavation zone shows the highest efficiency, since the dewatering requirements of the subsequent zones with lower excavation depths may be met simultaneously. The dewatering optimization can significantly reduce the number of activated pumping wells, total pumping rate and environmental effect.

Key words: confined water, dewatering optimization, cut and cover tunnel, linear programming, numerical simulation