Progression of backward erosion piping with sudden and gradual hydraulic loads

With the utilization of underground space, backward erosion piping (BEP) has been observed in many underground structures. Different from BEP in embankments or river dikes, the BEP in underground structures is usually triggered by a sudden flow of water and persists in a “progression phase,” in which the piping process can always reach an equilibrium before higher hydraulic loads are employed. In this study, the progression of BEP with sudden and gradual hydraulic loads was investigated using a radial Hele-Shaw cell. The test results indicated that the progression of BEP could be strongly influenced by the hydraulic loading speed. Once a faster hydraulic loading method was employed, the erodible medium could organize itself and show a greater resistance to erosion; additionally, the erosion pattern could be more uniform. These findings were included in a discussion of the erosion mechanism.