Predicting the amount of face seepage during the excavation of the mechanized tunnel, using numerical and analytical methods

Abstract

One of the usual problems during the construction of underground structures has been the water seepage into these structures. Water seepage into the tunnel, especially during excavation, could reduce the excavation procedure's rapidity and make the walls unstable. Furthermore, to embed the required pumps for draining leaked water into the tunnel, it is necessary to estimate the tunnel's approximate inlet flow rate. The purpose of this study is to estimate the flow rate in the width of the tunnel inlet portal of the second part of Isfahan metro line 2, which has been done using numerical modeling and matching the results with analytical models. Observation of the sensitivity analysis results showed that the two parameters significantly affect the inlet flow rate of seepage into the tunnel: (1) Soil permeability coefficient, and (2) Groundwater level. Finally, the seepage flow rate was estimated in high water and water scarcity seasons, compared with the analytical results. Comparative parameters of NSE and RMSE were used to estimate the differences between analytical and numeral methods. This estimation showed that Lei (Groundwater 37: 23, 1999), andLombardi (2002) could estimate the tunnel portal's flow rate.