Analytical approach for time-dependent groundwater inflow into shield tunnel face in confined aquifer

Prediction of time-dependent groundwater inflow into a shield tunnel is a significant task facing engineers. Published literature shows that there is no available method with which to predict time-dependent groundwater inflow into a tunnel. This paper presents a prediction approach for time-dependent groundwater inflow into a tunnel in both anisotropic and isotropic confined aquifers. The proposed solution can predict groundwater inrush from the tunnel cutting face. To obtain the time-dependent groundwater flow quantity, the concept of a horizontal-well pumping test based on the theory of a point source is adopted. Multiple factors, eg, drawdown, thickness of aquifer, conductivities, and specific storage, are taken into account. Both groundwater inflow to the cross section of a tunnel face in the y-z plane and total tunnel inflow are obtained. Based on the proposed approach, the time-dependent groundwater inflow to a tunnel can be classified as either a uniform or non-uniform flow. The proposed approach is applied to analyse groundwater inflow of 2 field cases: (1) Metro line No. 7, Guangzhou City and (2) an underground tunnel in Huizhou, Guangdong Province. Results show that the proposed method can predict the measured values, and drawdown-related curves are also derived. In addition, the calculated results also reveal that the effect of hydraulic conductivity k_z on the total groundwater inflow differs from that of hydraulic conductivities k_x and k_y and the thickness of the aquifer.