Experimental study on internal erosion and seepage in the foundation of a dike under variable water head.

Internal erosion is one of the main causes of dike failures. Their failure mechanism is related to the physical characteristics (distribution of particle size, permeability characteristics, clay content, etc.), stress state, and hydraulic conditions of the soil around the dikes. In this study, a series of erosion tests under different rising rates of the water head were conducted to study the internal erosion mechanism of a dike foundation under varying hydraulic conditions. It was found that different water head rising rates resulted in different internal erosion failure modes; furthermore, two critical values of water head rising rate were observed that decided whether erosion or piping occurred, and influenced the failure destructiveness of the internal erosion. Under the action of a continuous water head, the continuous failure through internal erosion occurred primarily in four stages. Moreover, under different water head rising rates, the change rules of the water head, seepage flow, and Jx–Q (average horizontal hydraulic gradient–seepage flow) curve were different. The mechanism of internal erosion and the critical hydraulic gradient could be determined based on the Jx–Q change characteristics. The backward erosion piping, based on the well flow model, suggested that the water head changing rate influenced the piping process. [ABSTRACT FROM AUTHOR]