Abstract:Hydraulic fracture in the core of earth-rock fill dam,which is related to the safety of the dam during and after impounding,is an unsolved important geotechnical problem in hydraulic engineering. By investigating the ability to resist hydraulic fracturing of the vertical soil core of the Nuozhadu Earth-rock Fill Dam(261.5 m in height) that is being built on the Lancang River in Western China,a new method based on fracture mechanics to compute and analyze the problem of hydraulic fracturing is introduced. In the computing and analyzing,many influence factors on hydraulic fracturing such as the crack giving water way to enter the core,“water wedging” actions induced by the water in the crack and singular stress state at the tip of the crack are considered. The propagation of the crack under water pressure is assumed to follow mixed mode I–II in fracture mechanics for the crack spreading may be induced by the combination of normal stress perpendicular to the crack surface and shear stress parallel to the crack surface. An isoparametric element with 4 nodes is employed in the finite element model of the crack and its influencing zone. A nonlinear hyperbolic model suggested by Duncan and Chang is used to simulate the stress-strain relationship of dam materials including soil core,rock shoulder,and rock cofferdam,etc.. A linear elastic material with lower Young¢s modulus is used to substitute for the crack. In order to investigate the ability of the core of the high rock-fill dam to resist hydraulic fracturing,two different cases are computed and analyzed,i.e. three imaginary horizontal cracks at the upriver surface of the core,and three vertical cracks at same levels. The computing results of the two cases indicate the ability of the core to resist hydraulic fracturing is considerable.