Abstract: A coupled particle flow code (PFC) and computational fluid dynamics (CFD) method was adopted to study the transport and loss process of sand under pipeline orifice seepage erosion and to identify the main factors influencing ground subsidence. Orthogonal tests with three levels were designed to conduct mesoscopic numerical simulations for five factors: pipeline diameter, orifice size, buried depth of pipeline, sand internal friction angle, and groundwater depth. The numerical simulation results show that sandy ground settlement exhibits a V-shaped funnel distribution, with subsidence expanding both horizontally and vertically over time. Range analysis and variance analysis of the orthogonal test results indicate that groundwater depth hw has the greatest and significant impact on subsidence depth. Specifically, greater groundwater depth correlates with reduced subsidence depth. The subsequent ranking of influencing factors is: orifice size d, internal friction angle  and pipeline diameter DN. Pipeline buried depth has no significant impact on ground surface settlement. Based on these findings, an estimation formula for ground subsidence range induced by pipeline leakage under various conditions was proposed. These results provide a reference for municipal pipeline design to mitigate ground collapse.

Key words: pipeline leakage, ground subsidence, PFC?CFD, numerical simulation, orthogonal test