Experimental study on confining pressure effect of hard rock indirect tensile test and mechanical mechanism

In order to study how the different loading conditions and confining pressures affect the style of rock fracture, an improved Brazilian disk device was firstly used to do same experiments. Several rules were obtained through the experiments with the marble and sandstone. Firstly, the peak stress and vertical strain were increased with the addition of confining pressure. However, the change of angle between pre-set crack and loading direction has little effect on the peak strength. Secondly, scanning electronic microscopy results demonstrated that the fracture morphology of rock influenced by confining pressure. With the low confining pressure, the proportion of tension zone in the specimen is bigger than shear zone and it changed when the confining pressure increased to a high level. Thirdly, the fracture toughness of rock is changed as confining pressure grows. (paper)