The Effect of Joint Number and Joint Angle on The Failure Mechanism of Mine Pillar

Experimental and discrete element methods were used to investigate the effects of joints number and joint angle on the failure behaviour of rock pillars under uniaxial compressive test. Gypsum samples with dimension of 200 mm×200 mm×50 mm were prepared. The compressive strength of model material was Within the specimen, imbeded joint were provided. The joint lengthn was 6 cm. in constant joint length, the number of joints were one, two and three. In experimental test, the angle of diagonal plane related to horizontal axis were 0, 30, 60 and 90 degree. In numerical test, the angle of diagonal plane related to horizontal axis were 0, 15, 30, 45, 60, 75 and 90 degree. The axial load rate on the model was 0.05 mm/min. the results showed that the failure process was mostly governed by both of the non-persistent joint angle and joint nubmer. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore 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 joint number. Finally, the failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods.