Abstract：Based on the mechanism of the interaction between geo-body and structural body，the nature and description method of irregular interface between geo-body and structural body are studied. A new cubic covering method is proposed to determine the fractal dimensions of the interface，which improves the measuring precision. The interface effects，such as the deformation，failure and slide of interface，are discussed for different interface shapes by using the photoelastic coating tests. The two-body(geo-body and structural body) mechanical model with the interface effect is established. The interface element with homogeneity and fractal distribution is developed in numerical simulation. The failure pattern and influential factors are studied based on the interaction between gravity dam and foundation，which objectively estimates the global stability of the dam. The propagation pattern of the irregular interface cracks at heel of concrete gravity dam is studied by using fracture mechanics. Critical length and loads of interface crack propagation are obtained using composite fracture criteria. The results indicate that the coarse interface prevents the propagation of interface crack，and redounds to stability of gravity dam.
