Investigation on Fracture Mechanisms and Crack Propagation Process of Natural Rock-Concrete Interface

Abstract

The tests of uniaxial tension and three-point bending are carried out on rock-concrete composite specimens with natural interfaces to investigate the interface mechanics and fracture process so that to establish interface tension-softening constitutive law between concrete and rock. Tensile strength, fracture energy and initial fracture toughness of rock-concrete interface are investigated qualitatively. Based on the load-displacement curves measured in three-point bending test, the energy dissipation at rock-concrete interface is derived using the modified J-integral method. Further, through enforcing balance between energy dissipation and energy caused by fictitious cohesive force acting on fracture process zone, the tension-softening constitutive law of rock-concrete interface is established, which takes into account the effects of fracture energy and tensile strength of interface. For the sake of practical applications, the tension-softening constitutive expression is simplified as a bilinear function. Finally, the crack propagation process of the concrete-rock composite beam is simulated numerically based on nonlinear fracture mechanics theory by introducing a crack propagation criterion. The predicted P-CMOD curves show a reasonable agreement with the experimental ones, which verifies the tension-softening constitutive law for rock-concrete interface derived in this study.