Experimental researches on effect of foundation structure on piping in multilayer embankment

The situations of the occurrence and development of piping are different because of different soil layer structures of embankment. Based on the laboratory tests, the destruction processes of piping of multilayer embankment with three kinds of different sand layers are simulated. By changing the grain-size distribution of the underlying sand layers, the effect of sand layers with different grain-size distributions on the mechanism and process of the occurrence and development of piping is analyzed. The test results show that when the sand layer of multilayer embankment is fine sand, it bears larger water pressure, and the critical hydraulic gradient is high. Once piping occurs, the seepage discharge, erosion mass and damage range are large. The piping failure of this kind of embankment is sudden and dramatic, and prevention measures should be taken as early as possible. When the sand layer is coarse sand, the situation of piping is like that of sand gravel layer. The damage scope of piping is confined to the top of the gravel layer, and the damage depth is limited. When the sand layer is fine gravel, the critical hydraulic gradient is small, the damage extent gradually increases, and the speed of piping is quick because large amount of erosion embankment can generate obvious seepage deformation.