RATE-DEPENDENCY OF TENSILE FRACTURE PROPERTIES OF ROCK-CONCRETE INTERFACE

The effects of strain rates (10⁻⁵s⁻¹ to 10⁻²s⁻¹) on tensile strength and fracture properties of rock-concrete composite specimens were studied. The tensile strength, load versus loading point displacement curve (P-δ curve), load versus crack opening displacement curve, initial cracking load and peak load of the interface under different strain rates were obtained by axial tensile test and three-point bending test. The critical crack propagation length was obtained by clip-gauges method and DIC method. The P-δ curve was used to calculate the fracture energy and the displacement extrapolation method was used to calculate the double K fracture toughness. The length of fracture process zone under different strain rates was obtained by analyzing the data of crack opening displacement. In addition, the characteristic length was calculated by considering the fracture energy and tensile strength. The results show that the fracture energy and initial fracture toughness increase with the increase of strain rate, while the critical fracture length and unstable fracture toughness increase as the strain rate is no more than 10⁻⁴s⁻¹, and then decrease as the strain rate is greater than 10⁻⁴s⁻¹. The length of fracture process zone and characteristic length decrease with the increase of strain rate. The rate effects of rock-concrete interfacial fracture parameters were discussed in three aspects: crack development path, free water viscosity and inertia effect.