Experimental Research on the Piping Development Process of a Typical Dike Foundation in Poyang Lake Area.

Dike foundation piping is one of the most important reasons for the dangerous situation and even the breach of dikes in Poyang Lake Area. It is of great significance to study and explain the disaster-causing mechanism of dike foundation piping in Poyang Lake Area from the mechanism so as to deal with the dangerous situation of piping and carry out emergency rescue scientifically.In this paper, an organic glass model tank is designed and manufactured, which integrates the functions of pore water pressure signal acquisition, seepage flow observation, erosion soil particle collection, graded constant head control, internal water circulation and so on. Based on the typical dike foundation structure of a dike in Poyang Lake Area, the physical model test of piping is carried out by using the prototype soil of dike foundation, and the whole process of piping occurrence, development and collapse of prototype multi-layer complex dike foundation is completely simulated. Combined with the experimental phenomena, the hydraulic conditions and soil particle erosion rate of the six stages (surface crack development stage, latent layer failure stage, overlying layer failure stage, piping channel upstream stage, embankment foundation failure stage, embankment foundation collapse stage ) in the process of piping occurrence and development are analyzed, and the special embankment foundation failure mechanism of the dike is explained by analyzing the effect of vertical seepage force.The results show that the piping failure in the dike foundation structure in Poyang Lake Area is concentrated in the underlying sand layer. Under the action of osmotic pressure, the overlying weak permeable layer is penetrated by seepage, and the piping channel is formed on the contact surface between the sand layer and the overlying layer, which accelerates the erosion of soil particles and eventually leads to the dike foundation collapse. The loam layer sandwiched in the clay layer in the embankment foundation of a typical dike in the Poyang Lake Area cannot play the role of the transition layer between the strong and weak permeable layers. The law of soil particle erosion is similar to that of the embankment foundation without the transition layer. The growth rate of the cumulative erosion of the soil particles forming the surface piping outlet and the embankment foundation cracking is less than 0.1 g/s; the average overall critical horizontal gradient of the dike foundation where piping occurs is about 0.1. [ABSTRACT FROM AUTHOR]