Fracture And Gradient Enhanced Damage Model In Interface Stress Element Method And Its Application In Engineering

Study of abutment failure is important in stability analysis of arch dam-foundation systems. FEM cannot effectively simulate the faults and joints in rock foundations. Considering this, interface stress element method (ISEM) is presented to simulate discontinuous interfaces in rock foundations, and furthermore to study stability of dam abutment and crack propagation. The main contents of this paper are summarized as below:Maximum energy release rate criterion is proposed to trace crack growth under various load-cases besides of Mohr-Coulomb criterion and maximum tensile stress criterion. Considering the characteristic of ISEM that the crack is concentrating on the interfaces, method of interfacial crack in bi-material is introduced in ISEM for the simulation of material characteristics and fracture behaviors.The damage variable is introduced into the constitutive relation of ISEM to describe the decrease of loading capability after yield. Fracture criterion based on rock materials are researched as well as its analysis method.The problem of mesh dependence in nonlinear calculation of ISEM is discussed and the gradient enhanced damage model is adopted on the basis of damage model. Nonlocal equivalent strain is introduced to the basic equations as another independent variable besides the displacements, thus iteration method of ISEM is constructed. Case studies are made, and through comparing numerical results with experimental results, the advantages of this method in avoiding mesh dependence are justified.With the convenience of ISEM in obtaining interfacial stresses, stability safety factor of sliding surface is deduced. The safety factors of critical blocks in dam abutments and foundations are checked, and the riskiest sliding surfaces can be searched.A program is developed and applied to 2D analysis of (1170 elevation of Xiaowan arch dam and 3D stability analysis of Jinping arch dam. Cracking and sliding in the riskiest sliding surfaces (e.g. faults, alteration zones, joints, etc.) and damage evolution are simulated, and stability safety factors of blocks in rock foundation are checked. With the comparison between numerical results and experimental results, the applicability of ISEM in analyzing arch dam – foundation systems is revealed.