Study Of Mechanism And Technology Of High-Pressure Fracturing Grouting In Roadway In 1000m Deep Coalmine

Under superposition of high ground stress and strong mining,surrounding rock of 1000 m deep roadway shows the characteristics of continuous rheology of surrounding rock,large deformation,overall movement,softening of coal and rock,closure of fissures,poor permeability of surrounding rock and so on.The traditional surrounding rock grouting modification technology under the condition of low stress and weak mining in shallow mine can not solve the problem of surrounding rock control of 1000 m deep roadway.Based on the specific engineering geological conditions of 121302 machine transportation roadway in Huainan Kouzidong Coal Mine,the research means of laboratory test,theoretical calculation of mechanics,numerical simulation,research and development of materials and technical equipment,field test were adopted in this paper.The key scientific problems such as the characteristics of crack expansion,the law of slurry seepage and the strengthening mechanism of grouting modification in the process of high pressure splitting grouting in 1000 m deep roadway been deeply studied.The research results are as follows:(1)The in-situ test and analysis of surrounding rock stress,surrounding rock strength and fracture structure of 1000 m deep roadway were carried out systematically,and the geomechanical characteristics of surrounding rock of 1000 m deep roadway were ascertained.The influencing factors and mechanism of poor injectability of surrounding rock in high stress and low permeability roadway were also studied.The results show that the difference of principal stress in 1000 m deep coalmine was large,and the higher principal stress difference promotes the development of cracks in coal and rock mass,the shallow breaking and development of surrounding rock of roadway,and the closure of deep cracks,which leaded to the low infiltration and diffusion range of slurry and poor grouting effect in conventional grouting technology.(2)The mechanical analysis model of crack initiation of high pressure splitting grouting in 1000 m deep roadway was established,and the crack initiation criterion and critical initiation pressure of borehole under impermeable and permeable conditions are deduced.At the same time,based on the theory of seepage mechanics,the numerical calculation model of seepage diffusion law of advanced high pressure grouting slurry in roadway was established,and the influence of surrounding rock permeability coefficient and grouting pressure on the seepage diffusion law were studied.The research results show that for the surrounding rock of soft rock roadway in 1000 m deep mine,the use of new modified grouting material and increasing grouting pressure to promote the re-opening and expansion of cracks been an effective way to improve the effect of grouting reinforcement of surrounding rock.(3)The crack propagation test of high pressure splitting grouting under true triaxial condition,the macroscopic mechanical strength test of high stress and low permeability surrounding rock splitting grouting reinforcement,and the microscopic electron microscope scanning and nano indentation test were carried out.The results show that different in-situ stress states made obvious influence on the initiation pressure and crack propagation shape of high-pressure splitting grouting.The bulk density and curing strength of grouting consolidation were increased with the increasd grouting pressure.Compared with the consolidation body under low pressure,the crack filling of coal and rock mass after high pressure grouting was denser,and the elastic modulus of slurry interface was higher than that of coal.(4)Based on the theoretical research results,a new type of ultra-fine modified grouting material was developed,and the matched high-pressure splitting grouting equipments were trial-manufactured,the maximum grouting pressure was up to40 MPa,and the high-pressure splitting grouting bolt and high-pressure splitting grouting technology were developed.A set of high pressure splitting grouting modification technology system for low permeability surrounding rock in 1000 m deep coalmine was formed.(5)The engineering test of high pressure splitting modification of surrounding rock of 1000 m deep roadway had been carried out in 121302 machine transportation roadway of Kouzidong Coal Mine.Through on-site detailed grouting data statistics,anchorage force test,borehole detection of grouting effect,the results show that the average initiation pressure of surrounding rock was about 26 MPa,and the field test data were consistent with the theoretical analysis.The new high pressure splitting grouting technology could been injected into the cracks at a minimum opening of about 2 ?m in the surrounding rock of a 1000 m deep roadway,and the deformation and failure of the surrounding rock had been obviously controlled.The problems of "injection" and "unanchoring" of low permeability roadway in 1000 m deep mine had been solved effectively.