Research On Coactions Of Piping And Collapse Of Soil And Its Simulation Method

The emergence and development of piping will form irregular cavity in the leveefoundation. The stability and collapse of the cavity may effect the piping development.The coactions of piping and collapse of soil over it may promote the development ofpiping or cease it gradually. To study the mechanism of the coactions, thecorresponding mathematical model and numerical simulation method, and to modifythe simulation program can provide more effective tool for piping developmentsimulation. The piping development rule could be revealed further by the simulationon models under typical conditions. For these purposes researches were performed asfollows.1. Soil arch effect is studied for homogeneous strata. The formula of the reasonablearch axis is derived with some approximation. The errors caused by approximationare analyzed. With the thickness of overlying soil and arch span known, the minimumarch height and minimum arch thickness in the homogeneous sand layer and in thehomogeneous clay layer can be obtained for stable soil arch. The variation ofminimum arch height with the thickness of overlying soil on piping zone and archspan is analyzed.2. For typical double-layer foundation under levee, soil arch effect is considered astwo situations: arch crest of the soil arch either lower or higher the interface betweenlayers. The arch parameters in typical double-layer foundation levee are obtained forstable soil arch, which could be applied to judge the stabilityof soil over piping zone.3. Finite element program-SDFEM compiled by Yangtze River Scientific ResearchInstitute is modified, so the coactions of piping development and collapse of soil overpiping zone can be simulated for uniform and double-layer foundation under levee.4. The development of piping in uniform and double-layer foundation is simulatedwith the modified program. The coactions of piping propagation and collapse of soilover piping zone are analyzed for uniform foundation with cut-off wall anddouble-layer foundation under levee.