Numerical analysis of longwall gate-entry stability under difference remains coal thickness

The ideal mindset of coal mine industries is to extract the maximum amount of coal possible from the coal seam resource. However, there is an absolute limitation when it comes to coal excavation depending on geological condition and the adopted mining method of each mine. As a result, there must be some remain coal thickness left. This can be beneficial for coal bed that is surrounded by weaker dominant rock as the remained coal can help improve the stability of any opening structure during the mining development and excavation. This research seeks to identify the optimum remain coal thickness (RCT) above and below the excavation in order to maximize the stability of the gate-entry and investigate appropriate support for gate-entry. With this in mind, a trial panel of an Indonesian coal mine, which is located in East Kalimantan, is selected as the research study area. This mine situated in weak geological condition, which is common for coal resource in this region. This paper use FLAC3D for numerical simulation. Preliminary result, show that the reduction of displacement on top and bottom of the gate-entry does not increase much when the RCT is left more than 1 m on both the gate roof and floor. This can be a great indicator for optimum thickness for remain coal. The outcome also shows that steel arch SS540 with 1 m spacing is appropriated for adopting in this trail panel gate support system. The result from this research is essential for developing mine design in this region as well as other coal resources that have a similar condition. This knowledge also allows mine design to have a better support system optimization compare to previous work, which did not consider the effect of RCT.