Numerical Investigation on Roadside Backfill Area Roof Failure Mechanism Subjected to Roadside Backfill Body: A Case Study

Abstract

In retained gob-side entry (RGE) of coal mining, the immediate roof above roadside backfill area (RBA) plays a key part in transferring the main roof load downward and transferring the roadside backfill body (RBB) resistance upon the main roof upward. Numerical investigation was performed to evaluate the stress distribution, deformation characteristics, and plastic zone distribution of the immediate roof above RBA based on a field case of RGE in a Chinese colliery. The double-yield model for gob, strain-softening Mohr–Coulomb model for RBB and strain-softening Mohr–Coulomb model for the roof above RBA were proposed to improve the reliability of the 3D global numerical model in FLAC3D. The numerical results of the calibrated global numerical model indicate that the vertical stress of the immediate roof above RBA shows a V-shaped distribution when the RBB width is less than 2.4 m. The horizontal stress of the immediate roof above RBA reaches the maximum when the RBB width is 2.0 m. The vertical displacement and horizontal displacement of the immediate roof above RBA positively are associated with the RBB width. In addition, the tensile failure area of the immediate roof above RBA, and the ratio of the tensile failure depth of the immediate roof above RBA to the tensile failure depth of the road-in immediate roof increases with the increase of the RBB width while the tensile failure depth of the immediate roof above RBA decreases. The proposed modeling procedure can be repeated in RGE to evaluate surrounding rock stability with different geological and engineering conditions.