Characteristics of Mine Pressure Behavior and Zoned Support Technology for Advancing Working Face in Ultra-Close Coal Seams

To address the issues of severe surrounding-rock failure and ground support component failure in advancing working-face driving roadways (AWFDRs) in ultra-close coal seams, this study used the 5202 air-return roadway in Huaye Coal Mine as a case study and for engineering background. Numerical simulation, theoretical analysis, and industrial application methods were adopted to analyze the laws of the dynamic evolution of vertical stress in such roadways. The mine pressure behaviors of AWFDRs in ultra-close coal seams were also clarified, thereby enabling the proposal of a solution; namely, zoned support technology. The results show that the 5202 air-return roadway, as an AWFDR in an ultra-close coal seam, exhibits five different characteristic behaviors of mine pressure zones during excavation. Zone 1 is influenced by the adjacent working-face mining under goaf; Zone 2 is influenced by the adjacent goaf lateral abutment stress under goaf; Zone 3 is influenced by the stress of the overlying solid coal; Zone 4 is influenced by the adjacent goaf lateral abutment stress under the overlying solid coal; and Zone 5 is influenced by stabilized stress under the overlying solid coal. The mine pressure behaviors of these zones were ranked, from most intense to weakest, as follows: Zone 3 > Zone 1 > Zone 4 > Zone 2 > Zone 5. Based on this, a basic support scheme was proposed, which involves using bolt–mesh–beam supports combined with shed supports under the goaf and bolt–mesh–beam supports combined with roof anchor cables under the overlying solid coal. Additionally, in Zones 1 and 3, roof anchor cables or rib anchor cables were supplemented as reinforcing supports, which were combined with the basic support scheme described above to form a zoned support scheme for the AWFDR. The analysis of mine pressure behavior and implementation of a zoned support scheme for AWFDRs in ultra-close coal seams provides technical and engineering references for roadway supports under similar mining conditions.