Abstract: Jointed rockmass contains numerous discontinuities. Many of them are not distinctly separated and have certain cohesive strength. The bonded interfaces enable the jointed rockmass to have a high strength. When subjected to the dynamic load, these discontinuities will debond, dissipating the strain energy accumulated in rockmass. The cohesive properties of the discontinuities govern the fracture energy of rockmass to great extent. The debonded interfaces significantly weaken the rockmass. The improved Xu-Needleman potential function can well describe the cohesive properties of cohesive discontinuities. Based on the improved Xu-Needleman potential function, the paper derives the cohesive discontinuities element. To simulate the cohesive discontinuities in a jointed rockmass, the cohesive discontinuity element is embedded into the element partition method, which allows an intact element to accommodate a discontinuity without introduction of external degrees of freedom. When the cohesive discontinuity element is identified to debond; it will be automatically replaced by a usual joint element to reflect the contact and the friction effect between the debonded discontinuities. The simulation example suggests the discontinuity element in conjunction with the element partition method is an efficient method to simulate the discontinuity debond and growth in the jointed rockmass. The perspective of the present method should be highly inspiring in simulating the failure behaviors of the jointed rockmass subjected to dynamic load.

Key words: cohesive interface, jointed rockmass, interface element, element partition method, numerical simulation