Study on mechanical mechanism of roof subsidence in gob side entry retaining under consolidated backfill mining

Based on the overlying strata movement behavior under consolidated backfill mining method,the stability of support along side the gob side entry and coal wall was analyzed and then the reasonable width of the support and length of the elastic plastic zone in the coal wall were deducted.Based on Winkler elastic foundation beam theory,a beam model in gob side entry retaining under consolidated backfill mining to analyze the mechanics of immediate roof was built.The No.9301 backfill mining working face in Tangkou Coal Mine was selected as the analysis example,where the three key parameters influencing the roof subsidence in the entry were determined,i.e.the elastic foundation coefficient of the support was 50 MN/m3,the width of the support was 3 m and the elastic foundation coefficient of the backfill body in the gob is 80 MN/m3.In such condition,the roof subsidence could be controlled effectively.In the meantime,combined with the monitoring results of convergence between roof and floor in No.9301 roadway of Tangkou Coal Mine,the filed measurement showed that the maximum convergence of roof and floor was 213 mm，the surrounding rock control in the gob side entry was effective.