Prediction and Management of Ground Water for Underground Works in Himalayas

Abstract

The Himalayan geomorphology guides important hydrologic systems recharging ground water occurrences. Ground water conditions mainly depend on origin and occurrence of precipitation. Prediction and managing ground water occurrences in mountainous regions is difficult due to inadequacy of data. From ground water levels in the wells and the natural spring discharge levels it is possible to construct the groundwater contour maps, showing the form and elevation of water table to some extent. Tunneling in complex geological set up exhibiting highly heterogeneous rock mass conditions can be problematic, which may lead to disastrous and significant delay if not adequately foreseen in mountainous regions. High displacements, stability problems and ground water inflows are common phenomena observed during tunneling through fault zones. Advanced methods of prediction and investigation/probing ahead of the face during construction are useful to minimize tunneling difficulties and apply requisite supporting methods. The influence of ground water during tunneling through high mountainous terrain poses problems during construction by any of the TBM, DBM or NATM methods. The paper addresses ground water investigation methods and targets for obtaining the key parameters for estimating the rock mass behavior, rock mass characteristics and criteria for the selection of appropriate construction methods, based on estimations.