Analysis of Influencing Factors of Roadway Stability and Adaptability Criterion for Gob-Side Pre-Backfill Driving

To reduce the loss of coal pillars between two adjacent longwall working faces, gob-side pre-backfill driving (GPD) procedure is suggested. This paper introduces in detail the principles and characteristics of the GPD procedure. Based on the arc triangle block (ATB) formed by the fractures of the main roof, the Winkel Elastic Foundation Beam model of the relevant rock strata structure is established and analyzed. The influence of the different breaking positions of the ATB of the main roof, the different geological conditions of the surrounding rock, and the parameters of the backfill body on the stability of the backfill body are analyzed. Also, the adaptability of the GPD procedure under any geological conditions is analyzed. The results show that the sensitivity of the aforementioned factors on the stability of the backfill from high to low is as follows: the thickness of the immediate roof, the elastic modulus of the main roof, the elastic modulus of the immediate roof, the thickness of the main roof, the thickness of the coal seam, the elastic modulus of the coal seam, the width of the backfill body, the buried depth, and the elastic modulus of the backfill body. According to the geological conditions of the Changcun Mine, it can be determined that if the fracture location of ATB of the main roof from the backfill is less than 5 m, the GPD procedure cannot be adopted. For this situation, the required strength of the backfill is high; the backfill is difficult to maintain, and it is prone to fracture failure. The GPD procedure cannot be used for all geological conditions. Before the GPD procedure is implemented, a pre-judgment must be made not to cause unnecessary losses.