Study On Crack Propagation In Rock-Concrete Interface Using DIC

Due to the mismatch in material properties, the bond interface between concrete dam and bedrock is always a weak link, and easily promotes crack-initiation under external effects, such as water pressure and thermal action. The crack at the interface always propagates along the interface or kinks into the bedrock leading to fracture. In order to prevent the existence of cracks to endanger the safety of the dam, the chatacteristics of the interface crack was studied by many scholars. And testing on the fracture process zone of rock-concrete interface is of great significance on studying the crack characteristics. Therefore, in this dissertation the FPZ of rock-concrete interface cracks was measured by the advanced technology methods (Digital image correlation method),and the fracture process was simulated by finite element method. Specific research contents are as follows:(1) Experiment study on the rock-concrete interface crack propagation under three-point bending condition by using DICThe composite specimens were made of rock and concrete with the size of 100 X 100X 500mm3 and the ao/D of 0.3. Through the results of experiment and DIC measurement can be known:the sliding displacement of the rock-concrete specimens accouts for 11% of the opening displacement roughly, which can be approximated as I mode fracture; The fracture process zone length of rock-concrete interface increases with the variation of load, and the length of fracture process zone decreases when increased to form the full frature process zone; And the ratio of the crack length and the ligament length is about 0.83 when reached the full fracture process zone.(2) Experiment study on the rock-concrete interface crack propagation under four-point shearing condition by using DICThrough testing on the fracture process zone of different II mode component proportion specimens by using DIC, the experimental results show that:The ratios of the sliding displacement and the opening displacement under each level of three specimens present three different trends.; The deflection values measured by LVDT and DIC are compared to verify the accuracy of using DIC measuring the interface crack propagation of rock-concrete.(3) Numerical simulation of interface crack propagation under two kinds of fracture formsThe I mode crack propagation criterion and the interface softening curve which has proposed are used in the simulation of I mode fracture, the numerical results are in good agreement with the experimental ones. This notes that the simulated method can be used to simulate the variation of rock-concrete fracture process zone; The evaluation criteria along the interface was applied on the simulation of Ⅰ-Ⅱ mode interface crack propagation. Upon the comparison with the experimental results, the numerical ones show good agreement on the loading-opening displacement curves. Therefore, it can be verified that the evaluation criteria can be used to simulate the Ⅰ-Ⅱmode interface crack propagation.