| The resourse of metal mine in our country becomes exhausted day by day, it isbecoming inevitable trend to speed up prospection and exploitation of complexwater-rich mine. The influence of ground water on mining safety, new mining methodbecome important research subjects. The actual project was taken as researchbackground, comprehensive research method of theoretical analysis, indoor and field,numerical simulation and field monitoring were used to revise the unreasonable partsof national standard ‘Standard for Engineering Classification of Rock Mass’. Theresearch findings were applied to Gujiatai iron mine. Roof deformation-controlling,improving surrounding rock stress, decreasing the perturbed mechanism and rule ongrouting curtain, parameter optimization and so on of new hexagon access miningmethod with cemented filling were studied systematically. Safety factor was leadingin as evaluating index of stability. The stability of surrounding rock under seepagecondition was studied to confirm reasonable scheme about multi-level andmulti-block. Based on the deformation and stress monitors of grouting curtain, therationality and feasibility of theory analysis were forecasted and testified to furtherimprove mining technology and provide technical support for mining safety. The maincontents and results are as follows:(1) The various problems of national standard ‘Standard for EngineeringClassification of Rock Mass’ were studied for corresponding methods, and theresearch results had been applied in Gujiatai iron mine. Based on inconsistentproblem of qualitative judgment and quantitative index, the basic quality index ofrock mass BQ was revised. The physical meaning of initial crustal stress formula isindeterminated, initial crustal stress should be divided into gravity stress and tectonicstress. The influence of gravity stress would be reflected by different safety factors indifferent depths to revise basic quality index of rock mass BQ. The safety factorwhich has strict mechanics content was used as quantitative criteria about stabilityestimation in grading standards, which made the surrounding rock classification morescientific. The mathematical relation between basic quality index of rock mass BQ and rock mass classification index RMR were built, the reducing method aboutphysical mechanical parameters based on BQ value was obtained based on theexperience formula between RMR value and rock mechanics parameters.(2) Combined with suggests of ‘Standard for engineering classification of rockmass’, the surrounding rock of different sections in Gujiatai iron mine had been madea comprehensive evaluation by means of field point loading test, wave velocity test,field jointing statistics, three triaxial test. The grades and physical mechanicsparameters of surrounding rock at different sections had been determined. Thephysical mechanics parameters of filling with different ratio were also determined.(3) The permeate characteristics of full stress-strain process had been revealedthrough transient permeability test on samples of grouting curtain. There were threestages in whole destroying process: quiet period, the internal fracture appear.Development period, microcracks grow, extend and link up quickly. Completepermeate stage, samples have compression damage, fracture link up and fractureplane appears. The peak value of strain-permeability coefficient curve lags behind thepeak value of stress-strain curve, which means that the rock failure is the direct causeof gushing water.(4) The analytical method was used to solve surrounding rock stress ofhexagonal tunnel. The mapping function from exterior domain of the unit circle togeneral shape hole was used to obtain mapping function of hexagonal hole. Incondition of uniform load γ Hin vertical direction〠λγ Hin horizontal direction andground load is zero, the in situ stress field (λ value) had great influence on stressdistribution around the hole. When λ is less than0.2, tensile stress appeared in theroof and gradually disappeared with λ value increasing. The finite element softwareANSYS was used to simulate conditions of different lateral pressure coefficient, thenumerical simulation results was consist with analytical solution, which proved thatthe analytic solution could been used in design calculation of mining parameters.(5) Combined with variety of strain, deformation and plastic zone of surroundingrock in traditional numerical analysis, safety factor was leading-in as stability estimating index. The effects of buried depth, surrounding rock parameters, aspectratio and the cross-sectional area had been systematically studied and compared withthe result of rectangular stope room with same conditions. The superiority ofhexagonal stope was summarized in limiting roof displacement and controlling holestress transfer. The reasonable stope spacing should be more than2times of stopewidth, the reasonable size of rib pillar and block under different mineral parameterswere determined. The stability of surrounding rock in whole block excavation hadbeen analyzed. The rib pillar positions were more easy to unstable.(6) The rationality of scheme about multi-level and multi-block had beenresearched. Without seepage conditions, the spacing of mining blocks at the sametime was at least one block plus two rib pillars at single level. When miningmulti-blocks at two levels, the spacing was greater than two blocks plus three ribpillars and the roof of block at second level should be fillings. The dip angle oforebody was only about30degrees, blocks at first and third levels were not in onesection, the mining scheme of three levels and multi-block could refer to the schemeof multi-blocks at two levels.(7) The stability of surrounding rock under seepage condition had been testified,the spacing of mining blocks at the same time was at least two blocks plus two ribpillars at single level. When mining multi-blocks at two levels, the spacing wasgreater than three blocks plus four rib pillars, and the roof of block at second levelshould be fillings. The dangerous locations where seepage field and stress field maychange suddenly have been counted to provide technical support for the follow-upremote monitoring system.(8) Based on above researches, the mutational area of seepage field and stressfield in grouting roof were confirmed, the field monitoring of stress, deformation andpore water pressure put into effect. The initial monitoring results indicated that thegrouting roof was in stable state. |
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