RESEARCH ON FRACTURE CHARACTERISTICS OF ROCK-CONCRETE INTERFACE WITH DIFFERENT ROUGHNESS

The roughness of rock-concrete interface has significant effects on its fracture characteristics. To investigate the fracture characteristic of rock-concrete interface with different roughness, six kinds of interface roughnesses were prepared by mechanically cutting grooves on the rock surface and then standard three-point bending fracture tests were performed to measure the fracture parameters of rock-concrete interface. The initial fracture toughness K₁ⁱⁿⁱ was computed by a numerical method, and interfacial fracture energy G_f was calculated by pertinent P-δ curve. Experimental results indicate that the final crack is along rock-concrete interface, which proves that the rock-concrete interface is unsubstantial compared with bilateral materials. When interfacial roughness changes from 0.676 mm to 2.028 mm, the initial fracture toughness of rock-concrete interface increases from 0.362 MPa·m^1/2 to 0.515 MPa·m^1/2 (increasing 42.3%) and the fracture energy of rock-concrete interface increases from 17.928 N/m to 47.802 N/m (increasing 166.7%). In addition, with the increase of the interfacial roughness, the initial fracture toughness increases continuously, while the mode I fracture energy increases first and remains unchanged.