Quasi-static loading strain rate effects on saturated limestone based on Brazilian splitting test

Based on the Brazilian splitting test, real-time acoustic emission (AE) monitoring and SEM observations, the influences of strain rate on tensile strength and deformation failure mechanism of saturated limestone specimens are investigated. The results show that: (1) Compared with the dry specimen, the tensile strength of saturated specimens has a reducing tendency and the decrease extent is about 15.99%. (2) The AE characteristics are also affected by the strain rate, i.e., the number of AE events increases as strain rate increases. (3) When the strain rate is smaller (3.0×10^-4s^-1 and 9.0×10^-4s^-1), the failure mechanism of saturated limestone specimens is that the crack propagates between mineral particles, thus the tensile strength is the smallest. When the strain rate increases to 1.5×10^-3s^-1, the failure mechanism is coupled of being penetrated and penetrating along mineral particles, so the tensile strength is medium. However, when the strain rate equals to 1.0×10^-2s^-1, the failure mechanism begins to penetrate mineral particles, then the tensile strength is the largest. Based on the experimental results, a discrete element method (DEM) PFC^3D is used to analyze the meso-mechanism of strain rate effects. According the simulation results, the following conclusions can be drawn: the load-displacement curves are brittle when the strain rate is small. When the strain rate is high, the load-displacement curves show a ductile response. The tensile strength increases linearly with the increasing strain rate. The boundary energy is positively correlated with the tensile strength, i.e., the larger the boundary, the higher the tensile strength. The energy of sample failure at the high strain rate and the number of micro-cracks are all greater than those at the low rate.