Overlying main roof breaking characteristic and its effect on the stability of gob-side entry

In this study, to figure out the deformation mechanism, a particle flow model was used to simulate the deformation of surrounding rock in a deeply buried entry. The fracture evolution, stress, and porosity of surrounding rock in the process of the main roof breaking, meanwhile, the displacement after entry being excavated were recorded and analyzed in the simulation. The results show that the main roof breaking is different from the ideally elastic–plastic simply supported beam for it has two more plastic zones on both sides of the beam and its support points tend to move. In addition, the stress reduction zone in the coal seam is about 10 m where the coal body and surrounding rock are almost completely broken and porosity is surprisingly increasing from 0.01 to 0.39 in coal and 0.23 in the main roof. The displacement concentrated on the ribs of entry, especially on the coal pillar. The continuous and large deformation that appears in the stress reduction zone results from the nearly completely broken state of the surrounding rock. The tradeoff between the stress reduction and the broken state of the surrounding rock should be considered when choosing the location of the gob-side entry.