Bearing Evolution Characteristics And Stability Control Of Narrow Coal Pillar In Section

Roadway protection with wide coal pillars and gob-side entry retaining provide an effective technical way to alleviate the tight situation of mining and connection,but there are also technical defects such as coal pillar loss and low recovery efficiency.Based on this,this paper puts forward a technical idea of adopting narrow coal pillar to protect roadway.Taking a 6.0m narrow coal pillar in double working faces of a thick coal seam as an example,this paper systematically studies the migration and evolution law of overlying strata in stope,the control principle of discontinuous weak face cutting top to protect roadway,the weakening mechanism of surrounding rock in dense drilling holes and the bearing evolution characteristics of coal pillar prestressed reinforcement,and establishes the technical system of discontinuous weak face cutting top to protect roadway and prestressed reinforcement of narrow coal pillar.By using theoretical analysis,numerical simulation,industrial test and other research methods,the migration and evolution law of overlying strata and the temporal and spatial evolution law of lateral surrounding rock stress in stope are mastered,and the mechanism of strong rock pressure in narrow coal pillar mining roadway is revealed Through roof cutting,the stress environment of surrounding rock of roadway and section narrow coal pillar is effectively improved,and the supporting resistance,vertical displacement and roof rotation sinking angle of section narrow coal pillar are determined according to elastic-plastic mechanics theory,which further explains the necessity of roof cutting and determines that the height of roof cutting is9.0m and the angle of roof cutting is 0.Secondly,the numerical simulation model of discontinuous weakening zone in dense drilling is established,and the development of pressure relief ring in dense drilling and the stress evolution characteristics of discontinuous weakening zone are studied The reinforcement mechanism of narrow coal pillars was studied by numerical simulation.The coupling relationship between the bearing characteristics of 5.0m,6.0m,7.0m,8.0m,9.0m wide coal pillars and support through anchor cables was studied in detail,and the coupling relationship between support strength through anchor cables-width of coal pillars-bearing evolution law of coal pillars was obtained.With the decrease of coal pillar width,the ratio of residual strength to peak strength decreases,and the failure of coal pillar may be more severe.With the increase of supporting strength of anchor cable,the failure characteristics of coal pillar are improved.The results of industrial application show that the peak stress after cutting the roof at 120 m of the solid coal side in 2312 roadway is reduced from 8.5MPa to6.0MPa,and the displacement of the cut and uncut roof and the approach of the two sides are reduced by 19% and 14%,respectively,which can effectively control the deformation of roadway surrounding rock and the stability of narrow coal pillars in the section,and achieve good technical and economic benefits.The paper contains 39 figures,9 tables and 77 references.