Size Effects on Fracture behavior of rock materials under combined tension-shear loading

The fracture behavior of cracked rock masses under combined tension-shear loading is an important issue for mining engineers in order to extract more efficiently or to prevent destruction of mines. Therefore, in this paper, the combined tension-shear fracture behavior of Gorveh marble is investigated experimentally and theoretically using the center cracked circular disk (CCCD) specimens of various sizes. The experimental results show that the fracture resistance of Gorveh marble increases by increasing the size of samples. As a result, in order to predict the fracture load of rock masses, the size dependency of the fracture resistance should be considered. Therefore, a new criterion is proposed to investigate the size effects on tension-shear fracture behavior of rock materials. The new criterion is a modified form of maximum tangential stress (MTS) criterion in which the higher order terms of the elastic stress field are taken into account. Finally, the fracture behavior for rock masses of Gorveh marble is predicted using the new criterion.