Amir Rezaei; Vahab Sarfarazi; Nima Babanouri; Mohammad Omidi manesh; Shirin Jahanmiri
Abstract
Non-persistent joints are geologic occurrences in rocks that weaken pillars because they are present within them. Using practical tests and numerical models, it has been determined how edge notches affect the way pillars break. Gypsum samples that are notched and have dimensions of 70 mm by 70 mm by ...
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Non-persistent joints are geologic occurrences in rocks that weaken pillars because they are present within them. Using practical tests and numerical models, it has been determined how edge notches affect the way pillars break. Gypsum samples that are notched and have dimensions of 70 mm by 70 mm by 50 mm are created. Gypsum's Young modulus, Poisson ratio, compressive strength, and tensile strength are 5.5 GPa, 0.27, 8 MPa, and 1.1 MPa, respectively. 10-, 20-, and 30-degree notch angles are used. The model receives an axial stress at a rate of 0.05 mm/min. On a rock pillar, numerical simulation is carried out concurrently with an experimental test. The findings indicate that the joint angle is mostly responsible for the failure process. The fracture pattern and failure mechanism of the pillars are connected to the compressive strengths of the specimens. At the notch points, two significant splitting tensile fractures spread vertically until coalescing with the top and lower boundaries of the models. On the left and right sides of the pillar, two rock columns are also taken out. The overall number of cracks rises as sample loading increases. The model's deformation at the start of loading reflect a linear elastic behavior, and the number of fractures steadily grows. When the number of cracks increases, the curve becomes non-linear, and the force being applied peaks. When the sample can no longer tolerate the applied force, a dramatic stress decrease occurs. The macro-failure over the whole model is what leads to the greater stress decrease following the peak load. In actuality, the reduced stress reduction is accompanied by more overall fractures. Similar findings are shown in both the experimental testing and numerical modeling.
V. Sarfarazi; H. Karimi Javid; K. Asgari
Abstract
The experimental and numerical methods were used to investigate the effects of joint number and joint angle on the failure behaviour of rock pillars under a uniaxial compressive test. The gypsum samples with dimensions of 200 mm × 200 mm × 50 mm were prepared. The compressive strength of ...
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The experimental and numerical methods were used to investigate the effects of joint number and joint angle on the failure behaviour of rock pillars under a uniaxial compressive test. The gypsum samples with dimensions of 200 mm × 200 mm × 50 mm were prepared. The compressive strength of the intact sample was 7.2 MPa. The imbeded joint was placed inside the specimen. The joint length was 6 cm in a constant joint length. There were several numbers of cracks including one, two, and three cracks. In the experimental tests, the angles of the diagonal plane with respect to the horizontal axis were 0, 30, 60, and 90 degrees. The axial load was applied to the model with a rate of 0.01 mm/s. In the fracture analysis code, the angles of the diagonal plane with respect to the horizontal axis were 0, 15, 30, 45, 60, 75, and 90 degrees. A constant axial load of 135 MPa was applied to the model. The results obtained showed that the failure process was mostly dependent on the angle and number of the non-persistent joint. The compressive strength of the samples was dependent on the fracture pattern and the failure mechanism of the discontinuities. It was shown that the tensile cracks were developed whithin the model. The strength of the specimens increased by increasing both the joint angle and joint number. The joint angle of 45° KI had the maximum quantity. The stress intensity factor was decreased by increasing the joint number. The failure pattern and failure strength were analogous in both methods, i.e. the experimental testing and the numerical simulation methods.
