Comprehensive analysis of disaster-causing characteristics of roof stress superimposed effect in steeply inclined coal seams

Aiming at the threat of dynamic hazards encountered by roof in Urmchi mine district,a numerical model was established by three dimensional explicit finite-difference program (FLAC3D ) with regional combination method based on mining layout and lithological characteristics. Meanwhile,the distribution characteristics of surrounding rock fracture and influence of mining disturbance were taken into consideration. And some relevant results indicated that the strike and dip pry-press function was generated with the deep coal-rock mass of No. 43 and No. 45 coal seam as supporting point. In addition,the superimposed effect of functions exacerbated the degree of roof stress. Also,the positions of roof stress of No. 43 and No. 45 were located,the bottom left and bottom right of corresponding working face separately, 20． 5 m and 13. 5 m away from corresponding south roadway respectively. Furthermore,the strike length of roof concen- trated stress area was 68. 2 m and 61. 5 m,and peak concentrated stress was located 28. 5 m and 25. 3 m before working face separately. Stress monitoring result showed that the concentrated stress of south roadway of No. 43 and No. 45 coal seam had a nonlinear variation tendency with roof concentrated stress,and the influence coefficient was 0. 52 and 0. 81 respectively. Therefore,roof concentrated stress can be calculated with influence coefficient,which is able to as- sess and predict the possibility and risk level of roof dynamic hazards. Prevention and control measures have been taken based on the research result and dynamic hazards have been controlled effectively,which has certain actual engi- neering significance.