Study On Surrounding Rock Control Technology Of Goaf Floor Roadway Under The Condition Of Close Coal Seam Spacing And Several Coal Pillars

The mining of underground coal resources usually adopts the long wall working face strike mining and the separation coal pillar is set between the working faces,but for the short distance multi seam mining,the engineering conditions of close distance and multi coal seam mining will be formed,and the goaf of the overlying coal seam will cause complex mining influence on the support stability of the lower mining roadway.Therefore,it is of great engineering significance to analyze the mechanical failure characteristics and study the support technology of the floor roadway in the conditions of close coal seam spacing and several coal pillars,which will provide a research basis and scientific basis for the study of surrounding rock pressure and support control countermeasures of similar engineering geological conditions in the futureTherefore,this paper takes the 14-2#coal seam centralized roadway in the Xinzhouyao Coal Mine as the engineering background,research on surrounding rock control technology of goaf floor roadway under the condition of near seam spacing and multiple coal pillars,through field investigation and analysis,numerical simulation analysis,mechanical theory analysis,industrial practice and other methods,the influence characteristics of mining instability of goaf floor roadway in the conditions of close coal seam spacing and several coal pillars,the control measures of roadway surrounding rock stability and the specific support optimization scheme are studied,the support effect is verified by field industrial test.The conclusions are as follows:(1)based on the field investigation and numerical simulation analysis of the 14-2#coal seam centralized roadway in the Xinzhouyao Coal Mine,the stress environment of goaf floor in the conditions of close coal seam spacing and several coal pillars can be roughly divided into two categories,and the two differences are:the mining stress concentration area under the goaf pillar and the mining stress reduction area under the goaf,and the two are alternately distributed;in the mining stress concentration area under the goaf pillar,the horizontal stress is obviously lower than the vertical stress,but the overall stress environment is relatively high,which leads to the serious stress damage degree of the roadway surrounding rock,but in the mining stress reduction area below the goaf,the horizontal stress is higher than the vertical stress,the overall stress environment is relatively low,and the stress damage degree of the roadway surrounding rock is relatively light;(2)through the mechanical analysis of roadway roof caving instability and roadway surrounding rock stress damage degree,it is concluded that the surrounding rock of roadway side under and near coal pillar bears heavy load,the roof fall and instability scale is aggravated by the failure of roadway side,however,the underground pressure under the goaf is relatively weak,it also needs to pay attention to the support control of roadway roof surrounding rock;(3)under the condition of close coal seam spacing and several coal pillars,the roof failure of goaf floor is connected with that of overlying goaf,at this time,the surrounding rock of roadway roof is not conducive to the active support effect of anchor cable suspension roof,and the anchoring effect of bolt is also limited,so the passive support is more effective than the active support;(4)the technical scheme of active and passive combined support of "anchor bolt+anchor cable+metal mesh+wood pile wall back filling+U-shaped steel support" is put forward for the 14-2#coal seam centralized roadway,and the feedback of support effect in industrial practice shows that the active and passive combined support technology can control the surrounding rock stability of the 14-2#coal seam centralized roadway well and meet the expected application requirements.