| Coal entry in deep usually belongs to soft rock engineering.After roadway excavation,coal entry in deep is difficult to support under the mining effect of coalface.The roadway generally has big deformation,roof fall in severe cases and causes casualties sometimes,and affects mine production.Most of the drivage roadway in Yujialing coal mine belong to classic soft-rock roadway in deep,the supporting problems of its district sublevel entry of coalface in deep are really serious.In the engineering background of broken head entry of 12808 coalface in Yunjialing coal mine,this dissertation employed field research,theoretical analysis,laboratory test,field observation,and industrial test to study the stability of broken coal roadway in deep,broken rock zone of surrounding rock,supporting theory of double shell bolt-grouting and integration of bolting and grouting technology.This paper used the numerical simulation to optimize the cross-section of the roadway and confirm the supporting parameters of bolts and cables in the double shell supporting scheme,which was performed in the industrial test in Yunjialing coal mine.The field observation showed,in the industrial test,the deformation of the surrounding rock decreased obviously,the force on the bolts and cables was good,which proved the optimized double shell supporting scheme and its construction technology was good for head entry of 12808 coalface.The main research results are as followed.1.Stability evaluation of coal entry of 12808 coalface 1.Stability evaluation of coal entry of 12808 coalfaceIn order to provide the basis for roadway supporting and confirming supporting parameters of roadway,it must be done to classify the stability of coal entry of 12808 coalface.This dissertation analyzed the stability of the roadway according to the mechanical parameters of rock from lab test and field observation results of broken rock zone.(1)Through uniaxial compression test,triaxial compression test,Brazilian test,this paper obtained uniaxial compressive strength,triaxial compressive strength,elastic modulus,Poision's ratio,cohesion,internal friction angle of the rocks from main roof,immediate roof and floor of the broken coal entry of 12808 coalface in Yunjialing coal mine.Based on the test results,this dissertation employed new fuzzy clustering analysis method to classify the surrounding rock of broken coal entry of 12808 coalface.It belongs to IV-class instability of roadway.Its classification provides more scientific basis for roadway supporting way and initial setting of supporting parameters.(2)The acoustic measurement and borehole observation instrument were used to observe the broken rock zone of head entry of 12808 coalface in Yujialing coal mine.The testing results shown,the scope of broken rock zone of roof was between 1.5m and 2.2m,the scope of left side was 2.7m-3.5m,the scope of right side was 3.0m-4.2m.The surrounding rock condition was bad,its stability was bad,which proved the correctness of the fuzzy clustering analysis evaluation results of head entry of 12808 coalface.(3)Based on the broken rock zone test results and field observation of the roadway deformation and failure,the main reasons for the roadway failure of head entry of 12808 coalface are as followed.The roadway has the characteristics of low compressive strength,unreasonable cross-section,lack of supporting strength,big load of surrounding rock caused by big broken zone and plastic zone.Aimed to the roadway with big deformation failure,this dissertation proposed double shell bolting-and-grouting supporting technology.This technology could reinforce the whole strength of shollow part of surrounding rock by bolt and grouting,could also reinforce the whole strength of deep part of surrounding rock by cable and grouting.2.Double shell bolting-and-grouting supporting mechanism of broken coal roadway in deep(1)Based on the engineering geologic condition and stability analysis results of surrounding rock of head entry of 12808 coalface in Yunjialing coal mine,this paper proposed the concepts of continuous double shell bolting-and-grouting model and non-continuous double shell bolting-and-grouting model,then analyzed grouting mechanism and full-size grouted bolt supporting mechanism.The grouting mechanism are reinforcing strength of surrounding rock,decreasing the broken rock zone,preventing the rock from weathering,improving the stress state of bolts and cables.Full-size grouted bolt(or cable)supporting mechanism are bonding the surrounding rock and bolts or cables into a whole,improving the shear strength of surrounding rock and decreasing the shear deformation.(2)Double shell bolting-and-grouting supporting mechanism of broken coal roadway in deep Based on elastic mechnics,plasitic mechanics and rock mechanics,this dissertation built up calculation model of surrounding rock deformation and failure of broken coal roadway to analyze the failure problem of the surrounding rock including broken zone,plastic zone and stress distribution.The radius of broken zone of the roadway is t times of that of plastic zone.The radius of plastic zone is given by The initial geostress is one of the main factors to affect the roadway stability.The other factors are cohesive strength,internal friction angle,the radius of roadway,etc.3.Numerical analysis of double shell bolting-and-grouting supporting scheme of broken coal roadway in Yujialing coal mine(1)This paper employed numerical simulation to analyze the effects of different cross-section on the roadway stability and choose the most economic and reasonable cross-section.The simulation results showed the arch-shaped roadway with tangent circle(2)This paper used FLAC3 D software to simulate and analyze the stabitlity of the coal roadway of 12808 coalface under the original supporting scheme or double shell bolting-and grouting supporting schemes.The simulation results showed,in the original scheme,the deformation of the roadway was much bigger,the deformation of roof and floor was bigger than that of two sides,the broken zone and plastic zone was much bigger and it was 5.1m deep in roof,the failure mechanism of surrounding rock is plastic shear failure.The stress on the bolts and cables exceed its own ultimate strength.The max.displacement,the thickness of the plastic zone in roof,the stress on the cables of the roadway with the original supporting scheme were much bigger than that of the roadway with double shell bolting-and-grouting supporting scheme.(3)Deformation and failure mechanism of surrounding rock of the roadway with original supporting scheme or double shell bolting-and-grouting supporting scheme(1)With the original supporting scheme,the surrounding rock of the deep soft rock roadway with big deformation had larger plastic deformation zone and broken zone,with the supporting of bolts and cables,the surrounding rock can not form stable deep shell supporting structure and high-bearing capacity of shallow shell supporting structure,so the roadway collapsed in the end.(2)The supporting scheme of the integration of bolting-and-grouting for coal entry of 12808 coalface could improve the mechanical property of surrounding rock of the rocadway,especially anchored zone of surrounding rock,realize the full-length anchorage of bolt and cable,obviously decrease the roadway deformation,and maintain the long-time stability of the roadway.Double shell bolting-and-grouting supporting structure includes shallow shell bolting-and-grouting supporting structure and deep shell bolting-and-grouting supporting structure.According to the acting mechanism of bolt,cable and grouting in the double shell bolting-and-grouting supporting scheme,this paper analyzed the scope of the double shell zone and its supporting strength.This scheme can realize grouting by bolt hole or cable hole.The thickness of the double shell and the scope of the anchoring surrounding rock depends on the length of the bolt or cable.The longer the bolt or cable is,the thicker the shallow shell and the deep shell are,and the bigger the cohensive strength and internal friction angle of the surrounding rock is.Namely,the anchoring surrounding rock reinforced by double shell can bear bigger external load.On the other hand,the supporting density of the bolts and the cables could improve the strength of the anchoring surrounding rock.The bigger the supporting density is,the bigger the internal friction angle and the cohensive strength of the double shell are,and the bigger the radial stress induced by bolt or/and cable is,which is helpful to provide the roadway stability.So,the sixth scheme had the best supporting effect with the longest bolt and cable and the biggest supporting density.4.Research on the construction technology of integration of double shell bolting and grouting for deep coal entry and its application effect(1)After continuous research and improvement in the construction technology of integration of double shell bolting and grouting,the grouting construction parameters and construction technology process were confirmed.(2)According to the statistical data of the deformation of roadway and the stress on the bolt and cable,the supporting scheme confirmed through double shell bolting-and-grouting supporting theory and numerical simulation results realized the roadway stability.(3)According to the statistical data of multi-point displacement indicators.TV Video record inborehole,and roadway deformation,the broken zone in the roof was about 2 meters,the broken zone in the roadway sides was about 3-4 meter.According to the pull-out test of bolts,the scope of the broken zone in sides was bigger than that of the bolts,the drawing force in the pull-out tests was up to 17 tones,which proved that the broken zone did not affect the anchoring force of the bolts too much. |
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