Laboratory tests on erosion of overlying sand layer on shallow and strong permeable stratum in dike (dam) foundation

There is local shallow and strong permeable stratum in dike (dam) foundation, and its head dissipating capacity is weak. It is easy to cause piping failure, and the failure mechanism still needs further studies. The erosion of overlying sand layer on shallow and strong permeable stratum in dike (dam) foundation is simulated by sand tank tests, by changing water block stages, observing phenomena of fine particle loss in sand, obtaining parameters of seepage discharge, seepage gradient, grain composition of soils and cone resistance. The test results show that piping failure occurs in the sand layer on shallow and strong permeable stratum when the water block stage increases to 48 cm. The failure process is divided into stages of steady seepage, internal erosion of fine particles, internal erosion of relative fine particles and piping failure expansion. Besides, the fine particles in sand are lost, the cone resistance of dike (dam) foundation decreases, and the foundation settles. The porosity and permeability coefficient of sand increase when the fine particles are lost, and the seepage and stress fields have great change. The reseach results may offer theoretical reference for dick (dam) foundation which contains shallow and strong permeable stratum.