| Gob-side entry driving is a great revolution in coal mining technology in China.It has a great impact on improving the recovery rate of the section,avoiding the influence of mining in the upper section,optimizing the rationality of mining and excavation connection.The roadway protection coal pillar can isolate the goaf and maintain the stability of the roadway,which is the main carrier of the bearing pressure of the upper goaf and the edge of surrounding rock.However,due to the influence of stress environment of excavation disturbance,the width and stress state of coal pillar,it is easy to lead to the instability of roadway protection coal pillar,damage of supporting structure,large deformation of roadway surrounding rock,which seriously restricts the safe and efficient mining of the mine.Therefore,the stability of coal pillar and supporting roof is the key to the support technology of roadway protection coal pillar in gob driving roadway.In this regard,based on Jining No.3 coal mine 123 lower 04 working face,to overcome the issues that asymmetric deformation of coal body and insufficient roadway side support resistance,the multi-dimensional synchronous control technology of roadway along the goaf was proposed.The deformation of roadway surrounding rock is controlled by three dimensions: jacking high-strength yielding pressure pillar supporting the roof beside the roadway,expanding and locking opposite through anchor cable bidirectional reinforcement of narrow coal pillar,and anchor mesh cable shotcrete roadway internal support.The theoretical inquiry,laboratory test,numerical simulation and engineering applications were applied in this thesis to analyse the gob-side roadway support structure and reinforcement mechanism,verify the support performance of jacking type high-strength yielding column and the two-way reinforcement effect of coal body.The research results were concluded as below:(1)Based on the structure model of basic roof arc triangular block,the stability of overburden fracture structure during excavation and mining was studied,and the influence of basic roof fracture position on the steadiness of coal body was clarified.In order to obtain the reasonable position of the goaf roadway and the determination method of reserved breadth of coal body,the distribution regular of the lateral bearing pressure of the surrounding rock of roadway was analyzed,and the destruction mechanism and stress state of the coal body were clarified.On this basis,it was calculated that the range of internal stress field in the coal body of 04 working face under 123 coal seam is 11.41 m,to ensure that the surrounding rock of roadway is arranged in the stress reduction area,and the reasonable breadth of roadway protection coal pillar is 3.7 m?6.21 m.(2)The roadway side retaining technology based on jacking type high-strength yielding column was proposed.Through the shrinkage bearing test,the pine was determined as the ideal pressure giving structure,the compression rate of pine is the highest,reaching 77.7%.On this basis,the axial compression test was carried out to study the bearing performance and failure characteristics of the strut under the influence of different length-diameter ratio and diameter-thickness ratio.Then,the cooperative coupling effect between the pressure-relief structure and the concrete-filled steel tubular column was analyzed,which has the property of“constant resistance shrinkable in the early stage and increasing resistance shrinkable in the later stage”,and the compression rate of pine wood exceeds 50%,and verified the reliability of the reinforcement measures at the grouting hole.Then,on the basis of experiment,the reduction coefficient of slenderness ratio of length diameter ratio of jacking high-strength compression column was modified,and the expression formula of the bearing characteristics of strut in yielding stage and stable stage was obtained.(3)Based on the structural design of inflatable lock-type anchor cable and the two-way reinforcement mechanism of narrow coal pillar,the pull-out test of inflatable lock-type anchor cable was carried out,and it was concluded that the maximum anchoring force of expansion lock body can reach 430 k N.On this basis,finite element simulation was used to analyze the bearing deformation law of coal pillar,internal stress distribution characteristics and force state of anchor cable under different reinforcement methods.The research showed that the large spacing of single row can reduce the bulging deformation of coal pillar under the reinforcement of inflatable lock-type anchor by 72.8%,and when the number of anchor cables is the same,the double row arrangement can better optimize the stress state of coal pillar and give full play to the mechanical properties of anchor cable.Based on this,the layout scheme of inflatable lock-type anchor cable in 04 working face under 123 coal seam was put forward.(4)The engineering application of gob-side entry driving in 04 working face under 123 coal seam was carried out,and the multi-dimensional synchronous control technology scheme of “double row inflatable lock-type anchor cable + jacking type high-strength yielding column”was put forward.The stability of surrounding rock of roadway can be ensured by the simultaneous construction of the three dimensions of reinforcing narrow coal pillar through anchor cable,supporting the overlying roof by jacking high-strength yielding pillar,and supporting the tunnel with anchor net cable and shotcrete,combined with “reinforcement mesh + air duct cloth to isolate the goaf” to meet the supporting surrounding rock of goaf roadway.The monitoring results showed that the bulging roadway surface displacement is about 80% lower than that in the unreinforced section,the separation value of two roofs is reduced by 63%,the average axial support force of coal body is about 1000 k N,and the shrinkage of pillar is more than 220 mm.The results of engineering practice show that the surrounding rock classification control technology can effectively improve the support resistance of roadway side,reduce the surface displacement of surrounding rock and ensure the long-term stability of gob side roadway. |
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