The Study On The Mechanism And Experiment Of Pre-filled Repeated Mining Of The Old Mining Damage Zone

In the 1980s and 1990s,because of lacking of technology and the limited equipment conditions,local small coal mines have long-term used knife column,lane column(high drop)and other backward mining methods.The recovery rate is less than 20%,resulting in a considerable more high-quality coal resources are not mined,left in the mined-out area,causing great waste.Implementation the old mining residues of coal exploitation again,that is also caslled residual coal mining.It can take full advantage of the valuable coal resources and create enormous economic benefits for the survival and development of resource-exhausted mine and safe production of the integrated mine,and it has important practical significanceThe background of this paper is based on the Coal Seam No.3 residual coal mining of Shenghua Coal Industry of Jincheng Anthracite Mining Group.On the basis of full analysis of the occurrence conditions of compound mining face of the residual coal,demonstrates the feasibility of high water material as grouting material,researches the fracture mechanism of grouting reinforcement of surrounding rock,designs of the grouting simulation test,analysis the flow rule of slurry in the scattered broken surrounding rock,uses the theoretical analysis to calculate the bearing layer thickness,put forward filling pre-filled mining scheme and implement the safe production of the complex mining face.The main work is as follows1,The application of field investigation,geophysical exploration,field reveal method and so on master the old mining roadways occurrence situation of Shenghua 1301 Coal Mining Industry.According to the characteristics of old mining area to classify them,this paper points out that the fallen coal and rock of the old mining is the main factors which influence the safety of second mining,so it is necessary to take measures before the second mining to ensure the stability of empty lane caving area when the coal wall reveals the empty roadway.Improving the integrity of the scattered broken surrounding rock is the key to the guarantee the safety of second mining2,According to the characteristics of the residual coal mining,this paper put forward the construction of the fill cutting layer and bearing layer,respectively established the impact damage and the static load limit damage as main bearing layer mechanical model.Based on the theory of the ultimate bearing capacity theory of sand foundation,the calculation formula of bearing layer under the action of impact can be gained by analyzing the critical thickness:h1=(Esmv2/Em?12-EmH01)/(2Em tan?+Esb1);based on JOHANSEN yield condition,the analysis for the bearing layer under the effect of overburden rock load critical thickness calculation formula is:h2=(?),the critical thickness of the bearing layer filling is 4.5 m after comprehensive analysis;it provides theoretical guidance for the second mining of the old mining caving zone3,According to the characteristics of the old mining area of cataclastic rock mass structural,combined with the three principles of grouting material selection,it can be decided to use high water material to grout the second mining area.By doing the slurry performance tests it can be known that high water material has low initial viscosity,injection can be good,be able to strengthen the gap of fallen scattered broken surrounding rock;at the same time,the super high water material can adapt to the underground environment,easy to be cut by the coal winning machine.The filling cost is low,and coal material increasing cost is 8 yuan/t.It demonstrates the feasibility of high water material can be used as the grouting material in second mining4,Through the cataclastic rock grouting simulation test,it is found that slurry flow in the crushed stone medium spread A cone-shaped divergence form,and the final stone body shape is an approximate cone body.The relationship among grout diffusion radius R and grout diffusion layer d,water cement ratio m,the coefficient of permeability k and grouting pressure P is:Q=0.6131·d1.4172·s-0.1534·k5.524·p0.4845;the relationship among grouting quantity Q,grout diffusion layer of d,water cement ratio m,the coefficient of permeability k and grouting pressure P is:P=6.60·s-0.6920·w0.215·p-0.0439;the relationship among stone body strength P,water cement ratio m,porosity w and grouting pressure P is:P=6.607·s-0.6920·w0.215·p-0.0439.Through super high water material in cataclastic rock grouting test,it can be known that the grouting concretion body strength mainly depends on the size of water cement ratio.Considering the intensity of the coal wall independence of the second mining,as well as economic benefit,it ultimately decides the ultra high water material appropriate water-cement ratio is 1:6?1:7,and it has important significance for predicting the grouting effect and the grouting parameter design.5,According to the distribution of old mining area in compound mining and the damage characteristics of the layered,progressive several rounds of grouting technology is put forward.On the basis of the theory of bearing layer filling and laboratory simulation of grouting,it designs the scene of the grouting parameters.Through the revelation of grouting area it can be seen that slurry can effectively consolidate the cracked coal and rock,and it makes the discrete rock masses to form a complete and stable induration.The working face of coal wall and the formation of the artificial false roof is in good integrity;it is neat after cutting the reinforced area,and grouting effect is obvious.