Comparative analysis on stress field distributions in roof cutting non- pillar mining method and conventional mining method

To explore the difference of stress field distributions in roof cutting non-pillar mining method and conven- tional pillar mining method,four numerical models,i. e. large coal pillar mining pattern (LCP),small coal pillar min- ing pattern with adjacent gateroad unexcavated (SCP Ⅰ),small coal pillar mining pattern with adjacent gateroad ex- cavated (SCP Ⅱ) and non-coal pillar mining pattern (NCP),have been built based on the first industrial test of NCP by roof cutting and pressure release. The difference of the stress field distributions in those four types of mining pat- terns are studied and analyzed. The results show that in front of the mining face,the influence of pillars has a limited range,where the vertical stress in these four mining patterns decreased orderly with the sequence of SCP Ⅱ,LCP,SCP Ⅰ and NCP. In the mining pattern of LCP,SCP Ⅰ and SCP Ⅱ,the abutment stress is highly concentrated around the gateroad. However,there is no stress concentration in NCP because the gateroad is canceled in this new mining pat- tern. At the side of mining face,the stress-concentrated position is in the large coal pillar in the LCP mining pattern, whereas the stress-concentrated position is in the integrated coal of next mining panel in the SCP Ⅱ mining pattern. The stress-concentrated positions of SCP Ⅰ and NCP are in the internal coal rib. As the pillar size decreases,the posi- tion of the peak stress becomes farther to the gateroad rib. The peak stress in LCP is the largest while that of NCP is the minimum. In terms of the peak stress,the peak value in NCP decreases by 18. 1% -20. 3% compared with that in LCP and 11. 8% -17. 3% compared with that in SCP Ⅱ. Moreover,when the roof is stabilized,the peak stresses in NCP and SCP Ⅰ are similar.