Analysis of the impact of groundwater-level decrease caused by drainage on tunnel water inflow

Affected by excavation, the phenomenon of groundwater-level drop around mountain tunnels is widespread, resulting in poor accuracy of the existing water-inflow calculation formula derived when the groundwater level is fixed. Based on this, a simplified calculation model of tunnel water inflow is constructed that considers drainage; and the tunnel water inflow is calculated according to the Dupuit assumption and conformal transformation. The law of conservation of fluid mass is used to solve the equivalent water head around the tunnel after drainage and the Taylor formula is used for degradation analysis, and the rationality of the model construction and the correctness of the formula derivation are verified through the tunnel under construction and numerical simulation. Finally, the sensitivity of the characteristic parameters is studied, the evolution law of the equivalent head is revealed and the influence mechanism is discussed. The research shows that the error between the calculated value of tunnel water inflow and the field measured value can be reduced from 16.1 to 8.9%, which improves the prediction accuracy of tunnel water inflow to a certain extent.