Investigating the interplay of holes and joints on crack propagation in mining pillars: Experimental and numerical insights

This study investigates how holes and joints affect the stability of mining pillars through both experimental and numerical methods, using gypsum samples measuring 5 × 20 × 20 cm. Four distinct models were developed, each featuring varying numbers and configurations of holes and joints. In each model, a key joint was positioned at angles of 0°, 30°, 60°, 90°, 120°, and 150° relative to the horizontal plane, which also influenced the placement of the other joints and holes. The samples underwent uniaxial compression testing in conjunction with numerical modeling performed using PFC2D software. According to the results, new tensile cracks were first observed at the tip of the key joint oriented at 60°. The presence of holes affected crack growth, leading to increased branching as the number of holes increased. Notably, at the 60° angle, the decline in mechanical properties was more pronounced with the addition of holes and joints compared to other angles. Conversely, the model with a key joint angle of 90° demonstrated the highest mechanical properties. The fracture patterns predicted by the numerical models were consistently validated by the experimental observations, confirming the reliability and accuracy of the computational approach adopted in this study.