Water Resources and Power

In order to study the nonlinear fracture process of rock in discrete element method,based on an exponential displacement softening contact model,numerical simulations of three-point bending tests were carried out on a series of geometrically similar edge-cut semicircular granite disks.The size effect of structural strength and the evolutionary characteristic of fracture process zone were analyzed.The shape of post-peak load-displacement curves shows that the gradual transition from ductile failure to brittle failure was observed as the radius of the semicircular disk increases.The simulated structural strengths match well with Baant size effect law.During the loading process,the length of fracture process zone increases at first and then decreases.Besides,it reaches the maximum length after the peak load is reached.This maximum value is highly related to the structural size.When the specimen size is large enough,the extension of fracture process zone is free of boundary and fracture process zone could fully develop to the saturated length.On the contrary,for small specimen,the extension of fracture process zone is restricted by boundary conditions.