Design Method Of Backfill With Superhigh Water Material And Control Analysis Of Surface Movement

Backfilling method is a advanced green mining technology adopted by more and moremine areas has been taken as a mature mining technology, which explore underground resourceutmost, protect the buildings on the ground effectively and prevent the ground water fromgetting into the shaft. Aiming at the problems of control surface subsidence with superhighwater material, the stress-strain relationship curves of different solidifying time and proportionwere studied by mechanics test, which tested the solid strength with different time andanalyzed relationship between strength and time in different proportion, and then the criterionof open-up backfilling roof control distance and design method were obtained usingelastic-plastic beam and plate theory under different mining conditions surrounding backfillworking face, which was proved accurately by practical surveying. The main results asfollows:(1) The stress-strain relationship curves of solidified superhigh water material withdifferent proportion and age were tested by mechanical experiment, which obtained thecompression strength and elastic modulus and provided an basis for projection application.(2) When the length-width ratio of face is b/a <1/2, the roof collapse distance can becalculated by beam model. The beam’s limit loading and limit collapse distance were obtainedby elastic-plastic with three kinds boundary supporting condition and analyzed the curves ofrelationship between length and elastic kernel height of beam section. Meanwhile, the limitloading and collapse were calculated by plastic limit theory at the condition of two-end-fixedbeam and one-end-fixed and the other simply supported beam; Considering the impact ofboundary conditions on practical calculation results, the expressions of beam’s maximumbending moment were further derived under the condition of elastic foundation beam andexisting horizontal pressure on it.(3) Aiming at different mining conditions surrounding working face with backfilling, theworking face was divided into5categories including no gob around, only one side existing gob,two side existing three side existing and gob on every side, which can be simplified asrectangle plate of four-side supported, three-side supported and the other simply supported,two-side supported and the others simply supported, one-side supported and three-side simplysupported, simply supported with four sides and the mechanical models were buildsrespectively.(4) Aiming at different mining and hard roof conditions around the working face withsuperhigh water material backfilling, the roof were taken as elastic plate with differentboundary supporting conditions. Based on virtual work principle, the deflection and momentexpressions of elastic foundation and existing horizontal pressure in two-way were deduced, the moment formula can be converted into single series by equivalent transformation, whichonly need six terms to meet engineering requirement. At the same time, the relationshipbetween driven distance and the maximum moment with different boundary conditions wereanalyzed, which provided an calculating method for design the width of working face withsuperhigh water material backfill mining when the roof was hard and different surroundingmining conditions.(5) Aiming at different mining and soft roof conditions around the working face withsuperhigh water material backfilling, the roof were simplified as elastic-plastic plate withdifferent boundary supporting conditions. In the light of plastic limit equilibrium theory, themaximum bending moment and limit collapse distance expressions of rectangle plate werededuced with different boundary support conditions and calculated the location parameters ofplastic yield-line, which provided an calculating method for design the width of working facewith superhigh water material backfill mining when the roof was soft and different surroundingmining conditions.(6) Aiming at different mining conditions around the working face, the laws of workingface width design were studied at the effect of different mining conditions, roof controldistance, roof lithology, roof thickness and payloads. When the working face around no gob,the width of it was largest, and when existing gob on every sides, the width was smallest, theworking face width were between them when other two kinds of gob existing way; the largerroof control distance, the weaker roof lithology or thinner roof and the bigger payloads, thesmaller design working face width, vice versa.(7) The effect on mining control with superhigh water material backfill was analyzed onthe basis of mining thickness, inclination, roof thickness, lithology, roof control distance,working face design width, driving velocity, solidifying time of superhigh water material andbackfill way, the designing method with superhigh water material backfill was formed, whichincluded the methods of determination roof control distance, working face width design,mining technology and choosing backfill way. Among them, the basis is the way ofdetermination roof control distance, the core is to design the width of working face, theprotection is to choosing mining technology and backfill method, which provided antheoretical and technical basis for working face design with superhigh water material backfill.(8) By choosing working face layout and the proportions of superhigh water material toadjusting the plate’s maximum moment to meet the roof no collapse of open-up backfilling atcertain mining and geological conditions, this method had been experimented at Taoyi andTianzhuang Mine. By means of observation station of surface movement, this way was provedto effectively alleviate the amount and velocity of surface subsidence if ensuring the backfilling ratio.