Numerical study of stability of mining roadways with 6.0-m section coal pillars under influence of repeated mining

Abstract

This paper presents the results of a numerical study of the stability of mining roadways in double-roadway excavation with a 6.0-m coal pillar. This excavation method is used to alleviate the imbalance between mining and tunneling and improve the recovery rate of coal resources. The roadways on both sides of the 6.0-m coal pillar were excavated before the mining activities, resulting in a complex stress environment of the coal pillar. A meticulously validated numerical model was developed to investigate the dynamic evolution characteristics of the 6.0-m coal pillar vertical stress and plastic state. The results indicated that the coal pillar entered the residual state and that the solid coal side of the next panel became the main bearing body under the abutment load caused by the mining activity of the 8311 panel. The abutment load transfer process from the 8311 gob to the 8312 panel exhibited obvious non-instantaneity. During the mining of the 8312 panel, an L-shaped high-stress area was formed at the upper end of the working face, owing to the superposition of the abutment load of two adjacent gobs. When the coal pillar transitioned from an elastic state to a plastic state, large deformation and failure occurred. To ensure roadway safety during the service period, the combined control technologies of (1) roof cutting using dense drilling and (2) support strengthening were proposed. Field observations indicated that the stability of the roadway next to the 6.0-m coal pillar was maintained and that the severity of other ground control problems was reduced.