Numerical simulation of the bubbling phenomenon ahead of the dam using a two-phase seepage free surface model

Abstract

The bubbling phenomenon that occurred in the Huangbizhuang reservoir has caused panic and concern, as it could potentially threaten the dam safety owing to the uncertainty of causes. In contrast to the general seepage problem, the challenges of studying the bubbling process include the description of the unsteady seepage free surface and consideration of gas compressibility. To investigate the seepage behaviours of the water–air two-phase and analyse the bubbling causes, an improved conservation level set-based two-phase seepage method is established. In this new method, the generalised Darcy's law is employed to obtain the seepage pressure and velocity fields of the water–gas phases. Furthermore, the physical properties near the interface zone are determined using a Heaviside function rather than the soil–water retention curve. Before modelling the bubbling phenomenon, the performance of the proposed method is validated using two benchmark examples. Simulation results of the bubbling process show that the generation, development, and release of pore gas pressure are the root causes of the bubbling phenomenon. Moreover, the water-storage process is a key factor that affects the occurrence and development of this phenomenon. In addition, the simulation results agree well with the actual observations, verifying the effectiveness of the proposed method.