Experimental shear test and Numerical investigation of the mechanical behavior of hollow plate rock-like materials with pre-cracks

In the current study, rectangular shape specimens containing holes and two-edge open flaws were prepared using gypsum to investigate the effect of defects on the shear failure behavior of rock-like material under different normal stresses. Firstly, three rock bridge angles were prepared. In each sample, the hole number was different, i.e., one hole, two holes, and three holes. To investigate the fracture processes of the samples, direct shear tests were carried out on them without the presence of the normal load. Concurrent with the experimental test, numerical simulation was performed on similar samples using a two-dimensional particle flow code, PFC2D. Secondly, numerical models containing closed notches and open holes were tested under three different normal stresses in a direct shear test. The material simulation was carried out using the Flat-Joint model and pre-joints are created as the Smooth Joints model. The results show that, in samples containing open notches, two tensile wing cracks started from joint tips while propagating in the direction of shear loading till joined with the hole boundaries. The rock bridge angles and the number of holes affect the failure pattern. The shear strength of models increased with the increase of both the rock bridge angle and the number of holes. In samples containing the closed notches, the failure pattern and shear strength were affected by the rock bridge angle, number of holes, and normal stresses. Also, the results show that there is an acceptable agreement between physical models and numerical models.