Analysis of internal erosion in granular soil during deep excavation with a Water-Inrush incident in a covered karst area

Abstract

Internal erosion of granular soil causes instability in the soil skeleton due to fine particles being washed out. Using the case of water inrush occurring in excavation engineering, the characteristics of the grain size distribution of the soil samples are analysed. Granular soil with a potential of suffusion is evaluated in detail. A practicable method including both prediction for the process of gradually updating the grain size distribution and calculation of the critical hydraulic gradients for the various particle sizes is proposed, which is based on the graded erosion principle. Consequently, a solution for evaluation of the flux rate and the erosion extent by hydraulic parameters of granular soils is concluded. A numerical model for the water inrush simulation is employed to validate the method. The results show that the solution is effective in both prediction of the water flux rate and evaluation of the internal erosion extent.