Modeling on the Prediction of Flow Rate and Groundwater Level Drawdown Associated with Tunnel Excation in Fractured rock

Groundwater level drawdown of the first stage resulted from groundwater leakage into tunnel was predicted by an analytical approximation. And numerical modeling was performed to predict the flow rates into tunnel and the groundwater level decline in the vicinity of future proposed tunnel area using a groundwater flow model MODFLOW. Groundwater level of the first stage was predicted to decrease by 15.3 m in analytical approximation. The flow rates in the total length of the future tunnel, when it is excavated, would be approximately in numerical model. The model predicts that the groundwater levels in the area around the future tunnel are expected to drop between 5 to 25 m relative to current groundwater levels. Under condition for a tunnel conductance increase, the flow rate was estimated to be and the groundwater level drawdown was predicted to be between 5 to 35 m The flow rate and the predicted groundwater level drawdown under a tunnel conductance decrease was estimated to be and between 2 to 12 m.