Dynamic evolution characteristic on stope pressure in whole life cycle of stope

The distribution and evolution characteristic of the stope pressure is a key factor to controlling sur-rounding rock in underground coal mining. The whole life cycle of stope is referred to the entire process from first cut to the ter- mination of mining operation in this paper. The stope pressure consists of two parts including the advanced abutment pressure and mining face roof pressure. Aiming to analyze the dynamic evolution characteristic of the stope roof pres- sure,UDEC simulation analysis and different surrounding rock mechanical models of over-lying strata at corresponding multi-time-space conditions were applied. It is demonstrated in this study that the maximum advanced abutment pressure occurs earlier under time dimension and spatial dimension,as compared with the mining face roof pressure during a single periodic weighting process. When the mining face has advanced to the critical extraction point,the advanced abutment pressure and mining face roof pressure reach their extreme value successively. Thus,the whole life cycle of stope can be divided into three stages,which are initial stage (Ⅰ),growing stage (Ⅱ) and stable stage (Ⅲ). The initial stage (Ⅰ) corresponds to the period from first cut to first weighting,in which the stope stress increases softly. The growing stage (Ⅱ) is from the periodic weighting to the critical extraction point between non-fully mining disturb- ance and fully mining disturbance. From critical extraction to the finish line is defined as stable stage (Ⅲ). During stage Ⅱ,the stope stress increases faster than that in stageⅠ,and during the last stage Ⅲ,the stope stress changes stably. According to the dynamic evolution of stope pressure featured in life cycle of stope,it could be used to predict the high stressed zone,and the reinforcement support or pressure-relief methods could be applied and adjusted in ad- vance,which can provide a safer mining environment.