Chain pillar optimization at a longwall coal mine based on field monitoring results and numerical model analysis

Chain pillars are designed to provide support to the gateroads that are subjected to changing loading conditions in a longwall coal mine. The pillar and gateroad stability is significantly sensitive to the in situ stress and extraction-induced stress caused by the longwall panel. This paper presents the monitoring results of surrounding rock deformation and ground subsidence during the extraction of a coal mine’s first panel. The monitoring period of the surrounding rock deformation starts when the extraction face is 150 m away from the monitoring site until the extraction face passed the monitoring site for 465 m. Panel-scale models were generated for estimation of extraction-induced loading which was then applied to pillar-scale models. The monitoring data set was used to validate the numerical models that simulate the abutment stress conditions and surrounding rock response of the entry. The validated model was then applied to further analyze the stability of the pillars for various optimization plans. This paper demonstrates the potential of the validated model to assist mine engineers to design and optimize the chain pillars in the longwall coal mine.