Water Inflow Prediction during Heavy Rain While Tunneling through Karst Fissured Zones

Abstract

A new method is proposed for water inflow prediction during heavy rain while tunneling through karst fissured zones. The proposed prediction method is a semianalytical and seminumerical method. First, an analytical determination method is put forth for a dynamic water pressure head. The main factors in the determination method include the surface catchment area, rainfall, porosity, surface infiltration coefficient, and initial seepage field (as initial pressure head and initial water inflow). Then a numerical prediction model is built based on the determination method of the dynamic water pressure head analysis. Stationary and time-dependent studies are used to solve the prediction model. Scenarios with both stable and variable rainfall are simulated. Results with stable rainfall indicate that water inflow always increases with rainfall, and water inflow under the smallest rainfall will first reach its limit. Variable rainfall is applied to simulate actual tunnel engineering. Variable rainfall is set through imitating an actual rainfall depth-duration curve. It is found that the trends of numeric and actual results are basically consistent. The water inflow reaches the peak point after a rainfall. The delay time of the numerical simulation results agrees with this under actual conditions.