Prediction of water–mud inrush hazard from weathered granite tunnel by an improved seepage erosion model

During tunnel construction, water and mud inrush disasters from completely weathered granite usually lead to the serious casualties and economic losses. Predicting these disasters are vital to the safety construction. Considering the critical erosion condition and flow pattern variation at the three stages (Darcy, rapid, and stable flow stages), a seepage erosion model is developed to perform the coupling analysis of water and mud inrush evolution. The model is shown to have favorable accuracy in real-time predicting the erosion region, ground settlement region, and the main hydraulic parameters (i.e., permeability, water inflow, and mud inflow) by comparison with the laboratory tests and field investigations. Then, effects of the model parameters (i.e., particle diameter, erosion coefficient, and ground permeability) on the water and mud inrush are investigated. Results show that (1) with the decreasing particle diameter, the permeability and the water and mud inflow increase gradually. (2) The erosion coefficient mainly affects the evolution rate and time of the water and mud inrush disaster. (3) The water and mud inrush can be controlled when the ground permeability decreased to the 0.2 time of the initial value. The research findings and the proposed model can provide the reference for the water inrush prevention in a similar project.