Experimental Study On The Mechanism Of Formation And Development Of Multilayer By Grouting Backfill Into The Isolated Areas Within Overburden

Grouting backfill into the isolated areas within overburden is a coal extractiontechnique to realize none-village-relocation, which can take full advantage of thestructure of overburden to control surface subsidence with fewer filling quantity. Thistechnology has been successfully used in many mining areas. The fromation anddynamic changes of multilayer correlate to the implementation of the grouting. Thus,the research of multilayer-forming condition and the dynamic variation rule todetermine grouting layer, to grasp the grouting time, to improve injection-productionratio would be significant.The analogous simulation experiment are used as the main investigative means,and use the project test proof on-the-spot for reference, the mechanism of formationof multilayer was obtained.Analogous simulation experiments show that: When there are typical key stratumwithin overburden, grouting with face advance can finally lead to the“Main groutingfilling horizon”form under this typical key stratum. And its grouting quantity make upmore than80%. The formation of “Main grouting filling horizon” is assurance to abetter control of surface subsidence. And simultaneously discovered when there is notypical key stratum within overburden or the key stratum has broken, its difficult toform “Main grouting filling horizon”, it become multilayer grouting, in this situation,the effect of surface subsidence control is undesirable.The engineering detection show that: When there are typical key stratum withinoverburden, the grouting horizon depends on the position of key stratum, the fillingbody concentrate mainly from bottom of the bore to bottom of adjacent key stratum.Its grouting quantity make up more than90%, this is so-called “Main grouting fillinghorizon”. In this situation, the effect of surface subsidence control is desirable, surfacesubsidence coefficient is0.1.In conclusion,“Main grouting filling horizon” embodied grouting in this area isfull and timely, in this condition, the effect of controlling surface subsidence is good.Injection match the demand of production is very important, if they don’t match eachother and the injection-production ratio is low, multilayer would be formed and keystratum may broken, the “Main grouting filling horizon” could not form.