Research on the breaking mechanism of bolts and cables in the gateway driven along a small coal pillar in the Datong mining area and the corresponding control technology

Abstract

The gateway of the thick coal seam working face in the Datong mining area was excavated along a small coal pillar, resulting in serious bolt (cable) breaking failure, strong surrounding rock deformation, serious ground pressure appearance, and difficulties surrounding rock control. So, the bolt (cable) breaking characteristics and corresponding causes of the 5106 return air gateway with a small coal pillar in Dongzhouyao coal mine (a mine in the Datong mining area) were analyzed through an on-site investigation, surrounding rock geotechnical parameters test, theoretical analysis, laboratory experiment, on-site engineering test, and other research means. The study carried out laboratory testing and analysis on the stress distribution characteristics and laws of the bolts, put forward the bolt (cable) breaking mechanism and prevention countermeasures, and completed the field industrial test of the surrounding rock pressure relief and support joint control technology in the gateway. The on-site tracking and data showed that the breaking conditions of the bolts (cables) were significantly reduced by improving the initial force of the bolts (cables), optimizing the supporting materials and components, canceling the pressure ring, and implementing the hydraulic fracturing top cutting and pressure relief + high prestressed full cable support technology. The displacement of the top and bottom plates was reduced by 51%, the displacement of the two sides was reduced by 46%, and the influence distance of the working face advance stress was reduced from 85 m to 30 m. The successful implementation of the study results in the small pillar gateway of the Dongzhouyao coal mine provided a reference for the promotion and application of similar gateway conditions in the Datong mining area.