Hydraulic fracturing of rock-fill dam

The condition in which hydraulic fracturing in core of earth-rock fill dam may be induced, the mechanism by which the reason of hydraulic fracturing can be explained, and the failure criterion by which the occurrence of hydraulic fracturing can be determined, were investigated. The condition depends on material properties such as, cracks in the core and low permeability of core soil, and "water wedging" action in cracks. An unsaturated core soil and fast impounding are the prerequisites for the formation of "water wedging" action. The mechanism of hydraulic fracturing can be explained by fracture mechanics. The crack propagation induced by water pressure may follow any of mode I, mode II and mixed mode I-II. Based on testing results of a core soil, a new criterion for hydraulic fracturing was suggested, from which mechanisms of hydraulic fracturing in the core of rock-fill dam were discussed. The results indicated that factors such as angle between crack surface and direction of principal stress, local stress state at the crack, and fracture toughness KIC of core soil may largely affect the induction of hydraulic fracturing and the mode of the propagation of the crack.