MPM Investigation of the Fluidization Initiation and Post-Fluidization Mechanism Around a Pressurized Leaking Pipe

Pipe leakage can induce soil fluidization resulting in severe consequences to the urban environment where underground buried pipes are extensively used. Soil fluidization is the process of transition of soil particles from solid-like to liquid-like behavior that can lead to the failure of the supporting ground and buried utilities. This paper applies the advanced two-phase double-point Material Point Method (MPM) technique to investigate the soil fluidization mechanism around a leaking pressurized water pipe embedded in fully saturated soil. In the model, the inflow water velocity leading to the initiation and evolution of soil fluidization around the leaking pipe is identified based on the changes in soil porosity and soil bed expansion ratio. This study shows that the MPM results are consistent with published experimental studies. Parametric analyses are presented to investigate the influence of different parameters, including the orifice size, bed height, and soil porosity on soil fluidization. The results show that the inflow velocity required for the onset and development of fluidization decreases with the increase in orifice size and soil porosity. The bed height increases the resistance of the soil bed against fluidization. The double-point MPM formulation is shown to be an effective and promising way to study soil-water interaction resulting from a leaking pipe. The model developed in this study can be used as a prediction tool to estimate the significance and progress of fluidization zone and to determine critical state that leads to ground failure. Such tool would be of significant value to asset managers that are responsible for maintenance of buried pipes, their supporting ground and surface transportation infrastructure.