Fracture mechanisms of rock-concrete interface: Experimental and numerical

Uniaxial tension and three-point bending tests are conducted on rock-concrete composite specimens with artificial grooving or natural interfaces to investigate the interface mechanics and fracture properties to establish an interface tension-softening constitutive law between concrete and rock for analyzing fracture failure of rock-concrete structures. Tensile strength, fracture energy and initial fracture toughness of a rock-concrete interface are obtained from experiment. Based on the load-displacement curves measured in the three-point bending test, the energy dissipation at a rock-concrete interface is derived using the modified J-integral method. Further, through enforcing a balance between energy dissipation and energy generated by fictitious cohesive forces acting on the fracture process zone, the tension-softening constitutive law of a rock-concrete interface is established, which takes into account the effects of fracture energy and tensile strength of an interface. For the sake of practical applications, the tension-softening constitutive expression is simplified as a bilinear function. Finally, the crack propagation process of a series of concrete-rock composite beams is simulated numerically based on a nonlinear fracture mechanics theory by introducing a crack propagation criterion. The predicted P-CMOD curves show a reasonable agreement with the experimental ones, verifying the tension-softening constitutive law for a rock-concrete interface derived in this study.The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China under the grant of NSFC 51478083, 51421064, and 51109026, and the fundamental research funds for the Central Universities under the grant of DUT14LK06