Abstract: To more authentically simulate the process of soil piping, the probable collapse of soil above piping zone should be taken into account. On the basis of soil arch theory and soil collapse mechanism, methods for judging the stability and the collapse of soil above the piping zone in the dyke of uniform foundation were presented. The numerical simulation method and calculation program were improved. By simulating the process of piping in the dyke of uniform foundation of non-cohesive soil and suspension-type cut-off wall, the rules of piping development in the presence of soil collapse above the piping zone were revealed. At the early stage, soil collapse does not happen; when the piping approaches to the cut-off wall, soil collapse occurs; when the piping bypasses the cut-off wall and develops toward the upstream, soil collapse has great influence on the path of piping. It is shown that the real failure zone would be larger than that in the numerical simulated results regardless of soil collapse. 

Key words: seepage, piping, collapse, cut-off wall, numerical simulation