Numerical modelling of longwall mining and stability analysis of the gates in a coal mine

This paper presents a novel numerical approach to simulate the longwall mining in detail, aiming to investigate the stability of gates and the loading process to rock bolts. The study site is the Svea Nord coalmine in Svalbard. In the proposed approach, progressive cave-in and fracturing of the roof strata, consolidation of the cave-in materials and stress changes are simulated in detail. The results of the simulations are used to analyse the loading process of the rock bolts in the gates. The numerical model is calibrated with the measurement data. The simulations reveal that the stability of the gates and the loading to the rock bolts are closely related to the width of the chain pillars. With slender pillars, shear displacements along weak interlayers and bedding planes results in heavy loading to the rock bolts. Therefore, the locations of weakness zones should be taken into account for rock bolt design. The proposed numerical approach can be used to find an optimal combination of the dimension of the chain pillars and the rock reinforcement in the gates.

► In this study an algorithm was developed for numerical simulation of longwall mining by FLAC(3D).
► Caving and fracturing of the roof stratum as well as consolidation of the caved materials are considered in the algorithm.
► The developed algorithm was implemented for the Svea Nord coal mine.
► The results of the numerical simulation are consistent with the measurement data.
► Stability of the gates and loading to the rock bolts are investigated by the numerical simulation.