Collapse characteristics and mechanisms of shallow cross roadways under mining blasting disturbance

Cross roadway collapses are a common occurrence in underground mining operations. While the influence of mining blasts on the stability of surrounding rock is acknowledged, the underlying mechanisms remain inadequately understood. This study investigates the characteristics and mechanisms of collapse in a shallow buried cross roadway subjected to mining blast disturbances, drawing insights from an engineering project in Anshan City, Northeast China. A strain-softening model based on unified strength theory was developed to effectively calculate and analyze the loosened zone thickness and surrounding rock displacement. The PFC^3D-FLAC^3D coupling method was employed to clarify the concentrated collapse area within the cross roadway, providing insight into the collapse mechanism through a cross-sectional model of the concentrated region. Results demonstrate that 50% of the cross roadway collapsed following the mining blast. Subsidence at the intersection was approximately one-fifth (0.66 m) of cross roadway's net height, exceeding subsidence in other areas by 1.3. Under the action of repeated mining blasting, the cross section of the connection roadway forms a semi-elliptical high tensile stress zone. After the cumulative damage of the surrounding rock of the connection roadway exceeds the ultimate yield strength, the cumulative stress release causes the tensile failure of the surrounding rock. The plastic zone of the connecting roadway expands to three times of the initial, and continues to develop. The surrounding rock on both sides experienced tensile stress, cumulative stress release, and the vertical propagation of tensile cracks.