Physical test and PFC modelling of rock pillar failure containing two neighboring joints and one hole

Experimental and discrete element methods were used to investigate the effects of both of the non-persistent joints and hole on the failure behaviour of rock pillars under uniaxial compressive test. Concrete samples with dimension of 150 mm × 150 mm × 50 mm were prepared. Within the specimen, two echelon non-persistent notches and one hole were provided. The hole was inserted at the middle of the specimen. two joints were distributed on the three diagonal planes. the angle of diagonal plane related to horizontal axis were 15°, 30° and 45°. The angle of joints related to diagonal plane were 30°, 45°, 60°. Totally, 9 different configuration systems were prepared. In these configurations, the length of joints was taken as 20 mm. diameter of hole was 20 mm. Similar to those for joints configuration systems in the experimental tests, 9 models with different echelon non-persistent joint were prepared in numerical model. The axial load was applied to the model by rate of 0.05 mm/min. the results show that the failure process was mostly governed by both of the non-persistent joint angle and diagonal plane angle. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. It was shown that the shear behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the joint angle. The strength of samples increases by increasing both of the joint angle and diagonal plane angle. The failure pattern and failure strength are similar in both methods i.e., the experimental testing and the numerical simulation methods.