Simulation of dewatering during construction of a bedrock tunnel, Nepean, Ontario.

Abstract

This thesis presents the results of groundwater flow modeling completed to simulate the effects of construction dewatering during the advance of a bedrock tunnel through an aquifer that serves as the source of water for numerous adjacent domestic water wells. The modeling was retrospective and consequently a large amount of data collected during the course of the tunnel project was available for the purpose of model calibration. Actual drawdown levels due to tunnel dewatering resulted in a significant number of well interference problems. The model was constructed through the application of standard groundwater flow modeling techniques using the United States Geological Survey's modular groundwater flow modeling program (MODFLOW), and was designed to provide a reasonable representation of the groundwater flow system within which the tunnel was constructed. The model simulated the tunnel as a drain which advances with time through the use of successive stress periods. An evaluation of grouting efforts that were undertaken to reduce the rate of groundwater inflow to the tunnel was completed. (Abstract shortened by UMI.)