Numerical Investigation on Urban Tunnelling under Groundwater Drawdown Condition – Impact on ground movement
In this paper the ground surface movement characteristics associated with urban tunneling in water bearing ground are presented based on the results from a series of finite element (FE) stress pore pressure coupled analysis. A hypothetical tunneling condition was considered with due consideration of urban tunneling situations. A 2D FE model, capable of simulating the relevant tunneling procedures, was adopted for analysis. Using the results, the ground movement mechanism caused by groundwater drawdown during tunneling was first examined. Also examined include the ground surface settlement and horizontal displacement characteristics. The results indicate that the tunneling-induced groundwater drawdown results in a deeper and wider settlement trough than without groundwater drawdown, and that the Error function approach does not yield satisfactory result in predicting a settlement profile when compared to the numerical prediction.