Fracture Characteristics Test of Precast Concrete Cracks Under Cyclic Loading

Taking on the retrofit abandoned laneway as compressed air energy storage system, we study the stability of its concrete lining under cyclic tensile stress. MTS-816 rock servo experimental system was introduced to cyclic three-point-bending test of notched concrete beam. Firstly, the average failure load and the average fracture toughness were obtained by the three point bending test under monotonic loading. Then, cyclic loading tests were carried out and fracture toughness was calculated. The test results show that: when the upper load ratio is 0.8, the peak COD(crack open displacement) curve can be divided into three stages, i.e. decelerated stage, stable stage and accumulation stage; when upper load ratio is below 0.8, the peak COD curve will get into stagnation stage after stable stage, COD no longer increases, crack no longer expands; the attenuation of fracture toughness of concrete is related to the upper limit of cyclic load. When the upper limit load ratio increases from 0.6 to 0.8, the fracture toughness decline rate increases from 0.8% to 12.7%, and the fracture toughness decreases significantly; otherwise, it does not exceed 0.8%, and there is basically no attenuation.