Ground response of entries driven adjacent to a retreating longwall panel

This paper presents an integrated approach for field instrument and numerical modeling to investigate the stability principle and control method of entries that are driven adjacent to a retreating longwall top coal caving panel. The test site is located in the city of Yuncheng, Shanxi Province, China. The instrument results indicated that the deformation and failure process of entries driven adjacent to the retreating longwall panel (EDRLP) could be divided into three stages: a slow initial increase stage (more than 125 m ahead of the mining panel), a rapid and continuous increase stage (125 m ahead of the panel to −100 m behind the panel), and an accelerating increase stage (−100 m to −200 m behind the panel). The stress changes in two ribs obtained with numerical modeling confirmed the described evolution of the mining disturbance. Meanwhile, numerical modeling results also suggested that a roof pre-splitting treatment could significantly decrease the peak stress in the coal pillar and panel rib, thus decreasing coal/rock mass failures and entry convergences. Furthermore, based on the rock formation condition of the test site and the ground response of entries, the detailed parameters of the roof pre-splitting treatment were determined and tentatively applied in the field. The field application suggested significantly improved gateroad performance with the proposed roof pre-splitting scheme. This study's results can help to increase understanding of the ground response of the EDRLP and correlations with roof strata movement. In addition, the proposed control strategy and design principle of the roof pre-splitting treatment can potentially be applied to other projects.