Study on Pressure Relief Mechanism of Hydraulic Support in Working Face under Directional Roof Crack

Abstract

When mining coal from the working face, the main roof withstands the overlying strata. The main roof's first weighting and periodic weighting may cause accidents, such as crushing the working face hydraulic supports. A mechanical model of the main roof was constructed, and the contributing factors of first and periodic weights on the main roof were examined in order to prevent such accidents. The thickness of the main roof was found as the most contributory factor to the main roof's stability. Therefore, a new directional roof crack (DRc) technique is proposed, which produces directional cracks in the main roof through directional blasting and makes part of it collapse in advance so as to reduce the thickness and relieve the first and periodic weighting. To verify the effectiveness of DRc, the mechanism of DRc was analysed. A mechanical model of the hydraulic support was constructed, and the DRc techniques were tested on-site. Field experiments with a complete set of monitoring schemes showed that, with DRc technology, the roof periodic weighting interval decreased by 35.36%, and the hydraulic support pressure decreased by 17.56%. The theoretical analysis was consistent with the measured results. Therefore, the DRc technology is feasible and effective to ensure mining safety at the working face.keywords: directional roof crack; pressure relief mechanism; main roof; hydraulic support pressure 1. introduction coal, the primary energy source in china, has had a profound impact on the country's social and economic development. globally, china is the world leader in coal production and consump-1 chinA univERSiTY oF Mining & TEchnoLogY (BEiJing), STATE KEY LABoRAToRY FoR gEoMEchAnicS AnD DEEp unDERgRounD EnginEERing,

Dip-Angle-Effect-Based Deformation and Failure Law of Steeply Dipping Stope Roofs with Large Mining Heights

“…The mine pressure behaviour law [9][10][11][12][13], roof spatial structure and its loading mechanism [14,15], asymmetric deformation and failure law of roof strata [16][17][18], stress transfer path and evolution mechanism [19][20], main roof fracture mode and evolution process [21,22], interaction law between surrounding rock migration and support [23][24][25][26], stope gangue slip filling effect, and overlying rock movement mechanism [27,28] under various mining conditions of steeply dipping coal seams have been studied through theoretical analyses, field measurements, and numerical calculations. The results of these studies have laid the foundation for mining theory and technology of steeply dipping coal seam.…”