Study on fracture characteristics of marble under monotone and cyclic loading

Based on the laboratory basic mechanical tests of marble, the PFC3D was used to obtain a set of mesoscopic parameters reflecting the characteristics of marble. Monotone and cyclic loading of cracked chevron notched Brazilian disc(CCNBD) model were carried out respectively to study the stress distribution, fracture toughness and crack propagation law of marble under different loadings. The results show that the mode-I(tensile) fracture toughness(KIC) of marble under two types of cyclic loading have different amplitude reduction of the static KIC, and the specimens have clear tensile softening zone after the post-peak region, and subcritical crack propagation occurs. Under cyclic loading, the crack growth of the sample can be divided into three stages: initial stage, stable stage and accelerated stage. At the initial stage of loading, the number of microcracks increased significantly, and the crack growth rate was stable. At the stable stage of loading, the crack growth rate gradually decreased, and finally, the crack growth rate gradually increased, and the number of cracks increased rapidly until failure. The tensile chain distribution was more concentrated at both ends of the ligament and on both sides of the disc than the monotonic loading. © 2019, Science Press. All right reserved.