Supporting a Retained Gob-Side Entry Under Soft and Fractured Rock: Computer Simulations and a Practical Example

This study uses theoretical analysis, finite difference numerical simulations with FLAC3D software, and a field test to determine and demonstrate the most reasonable width for a retained gob-side entry and the most reasonable dimensions for filling bodies to support that entry under soft and fractured rock. The paper proposes a set of technical measures to maintain the retained roadway. These measures are a combination of: (1) enhancing the strength of the rock surrounding the roadway with coupled bolt–mesh–anchor supports during excavation; (2) reinforcing the roof support in the backfilled area with bolts and wire mesh before the gob-side entry is re-entered; and (3) using single hydraulic props followed by concrete and gangue as roadside backfill to support the gob-side entry roadway. For the particular case considered in this study, a field trial at the 1702 face in the Zhaoguan Coal Mine, China, has verified that the proposed measures are effective. The field test results indicate that deformation around the retained roadway driven under soft and fractured rock has been effectively controlled. The maximum roof to floor convergence was no more than 450 mm and the lateral deformation of the roadway’s sides was less than 300 mm, much less than the deformation at the unreinforced 1704 face in the same mine.