Abstract:

Study with numerical simulation method and field measurement of broken rock partition is done on position design and support manners of open-off cut with large section in extremely close range seam. Numerical simulation shows that, more severe stress concentration influence range extends 4 meters and 3meters down on coal pillar side of upper coal seam；range of floor failure depth is of 5.6 meters, and a more complete rock range is from 3.3 to 5.6m；thereby along the upper coal strike the open-off cut position is at least 5 meters from the edge of stope. Broken rock partition tests show that the roadway roof separation fractured, more than 1.8 meters above is a serious rupture area where is not conducive to bolt anchoring；coal rupture area inner 1.5 meters from two roadway sides is the integrity of the regional coal；in order to use the length of the bolt effectively, the top and side design anchor length is 2 meters. The face open-cut construction proved combined support of anchor fore-poling and shed in the large section is successful, the economic and social benefits are significant.

Key words: Ultra-close multiple seams, Open-off cut, Stress distribution, Numerical simulation, Broken rock partition