Analysis of Gateroad Stability in Relation to Yield Pillar Size: A Case Study

This paper presents an integrated approach for field test and numerical modelling to investigate the relationship between gateroad stability and yield pillar size. The test site is located at Yuncheng city, Shanxi Province, China. Field tests indicated that when the yield pillar width was 17 m, the total convergence of the roof, yield pillar rib and virgin coal rib were 882, 587 and 352 mm, respectively, and severe roof sagging and yield rib spalling occurred during the panel retreat. A meticulously validated numerical model, incorporating a double-yield model for the gob materials and calibrated parameters, was developed to investigate the stress changes and yield zone distribution across the yield pillar with different sizes. The results of the simulation indicate that a yield pillar 17 m wide puts the gateroad in a high-stress environment; conversely, a yield pillar 8 m wide is subjected to a relatively low load and puts the gateroad in a good stress environment. Consequently, the rational yield pillar width was estimated at 8 m, and a support strategy was proposed. Field measurement data demonstrate that the newly designed pillar size and support pattern can efficiently ensure gateroad stability. The proposed numerical simulation procedure and calibrated method could be a viable alternative approach to yield pillar design. In addition, the design principle and support strategy for the yield pillar presented in this study can potentially be applied to other similar projects.