Assessment of mode I fracture of rock-type sharp V-notched samples considering the size effect

Abstract

In the present paper, the pure mode I fracture resistance of rock-type sharp V-notched (SV-notch) specimens with different sizes was investigated utilizing the MTS-FEM criterion. This criterion is a modified form of the maximum tangential stress (MTS) criterion and based on finite element method (FEM). According to the MTS criterion, when the maximum tangential stress at the critical distance from the notch border reaches a critical value, the onset of fracture occurs. As the critical distance in rock is relatively large, it is proposed in the MTS-FEM criterion that the tangential stress component at the critical distance is determined directly from finite element analysis. Moreover, it is well established that the critical distance in rock depends on the specimen size. Therefore, the size-dependency of the critical distance is considered in the present study. To evaluate the MTS-FEM criterion by considering size effect, some Brazilian disks with four various radii and central SV-notches were tested under pure mode I loading. It is revealed that, similar to cracked samples, the fracture resistance of SV-notched samples increases for large samples. Furthermore, it is shown that the MTS-FEM criterion is able to predict the notch fracture toughness of SV-notched rock samples by taking into account the size effect very well.