Numerical study on Brazilian splitting of heat-treated sandstone under different contact angles

Based on the particle flow code (PFC), the Brazilian splitting of sandstone treated at 25-1000 degrees C under different contact angles (2 alpha = 6 degrees-30 degrees) was carried out to study the stress distribution and fracture mode, and the Brazilian splitting was compared with the direct tensile test. The results show that: 1) The surface contact loading can reduce the end effect in Brazilian splitting. During the loading process, tensile cracks appear in the middle of the disc firstly. With the increase of the load, the tensile cracks converge and connect at the central part of the disc, and then extend to the end of the disc. 2) The tensile strength measured by Brazilian splitting at point contact of flat plate is less than that of direct tensile strength. The correction coefficient k of the tensile strength calculation formula decreases linearly with the increase of temperature 7', satisfying k = -3.303x10(-4)T+1.468. With the increase of the contact angle, the tensile strength of the Brazilian disc increases after heat treatment of different temperatures. 3) When 2 alpha >= 18 degrees, the Brazilian disc can guarantee to have a central crack initiation. When 2 alpha = 18 degrees-24 degrees, the fracture mode of the disk keeps unchanged at different temperatures. The disk will develop an inclined crack at a lower temperature (<= 600 degrees C) when the contact angle is too large (2 alpha = 30 degrees) Combined with the correction coefficient and the fracture mode analysis, the contact angle is recommended to be 18 degrees-24 degrees and the correction coefficient is between 0.802 6 and 0.856 0. It can ensure the center crack initiation and the stability of the fracture mode at different temperatures.