Variations of entries and bolting technologies, a case study based on a field monitoring of a longwall face

Roadways adjacent to a mining face are crucial for ensuring safe production, transportation, and the security of personnel. Nevertheless, the anchoring mechanisms and the integrity of the surrounding rock structures of these roadways have frequently been underestimated in mining endeavors. This study, using Xin'an Coal Mine in Gansu as an example, conducted an in-situ analysis of four anchoring methods to examine the axial force fluctuation characteristics and mechanisms of cable anchorage during coal mining. It was found that the lagged prestressed full-length anchorage demonstrated the most effective control. Subsequently, the study revealed the periodic subsidence phenomenon of roadway roofs on both sides of the working face, which is closely associated with periodic weighting. Based on monitoring results, the roadway roof was divided into three zones-'Peak Zone,' 'Valley Zone,' and 'Transition Zone'-using the periodic weighting intervals as units. Finally, the study employed a time-space detection method to observe the development pattern of roadway roof cracks and delamination during the coal mining cycle. The validation results indicated a low accuracy rate for this method. Additionally, the study discussed the applicable conditions for lagged prestressed full-length anchorage, measures to address roof subsidence in the 'Peak Zone,' and considerations for improving the time-space detection method. The research findings offer new insights into the impact of neighboring engineering disturbances on underground space engineering.