Numerical Simulation of Seepage Failure of Sandy Soil Between Piles Induced by an Underground Leaking Pipe

This paper presents a numerical study of erosion–slippage failure of soil between piles caused by underground pipe leaking using the coupled CFD–DEM (computational fluid dynamics–discrete element method) approach. By tracking the change in particles migration and flow fluid during numerical simulation, the development mechanism of erosion–slippage failure is clarified on both microscopic and macroscopic scale. Three stages during this failure (initial, developing and failing) are proposed, and the definition of critical water pressure at leaking hole is confirmed by the comparison of particles and fluid field. Four crucial factors for soil to resist erosion–slippage failure are discussed: pile spacing, degree of density, soil–pile friction coefficient and soil gradation. Pile spacing has the most obvious influence on anti-erosion ability of soil. The degree of density determines whether the erosion–slippage failure happens in an instantaneous way or a continuous way. The increase in friction coefficient can enhance the resistance of soil to erosion to small extent. Soil gradation shows a great influence on migration of fine particles and strength of soil structure.