Experimental Study Regarding Longwall Face Which Is Under The Old Goaf By Grouting Backfill Into Isolated Areas

The theory of grouting backfill into isolated areas are mainly by design reasonable cut mining width and setting up relative width of separate pillar,make full use the self-supporting capacity of surrounding rock on the roof.By backfilling to the drill hole on the ground with high pressure,the compacted grip zone will generate in the middle of the working face which can give a support together with key stratum structure.It will decrease the surface subsidence and get the achievement of none-village-relocation.This technique is used without too much experience repeated coal-mining.Nevertheless,repeated coal-mining is more normal with great influence to surface subsidence.The significance obviously is there for longwall face which is under the old goaf by grouting backfill into isolated areas.Numerical simulation is the main research method for the thesis.Also,some measured data is also combined here.By that,it has been obtained the conclusion of surface subsidence regularity of both repeated and un-repeated coal-mining by grouting backfill into isolated areas.The results show that the 7 coal effect of surface subsidence control in the long wall face of single coal seam under the condition of non repeated mining.In the control of the same injection production ratio,non repeated mining under the conditions of coal seam overlying surface rock grouting after isolation of maximum subsidence value is 201 mm,while in the repeated mining conditions for the existence of a single overlying coal seam goaf,then strata isolation grouting filling mining,the maximum surface subsidence to 282 mm,although the sinking of a certain increase,but compared with non repeated mining conditions did not change significantly,namely the implementation of overburden isolation grouting filling difficulty does not appear essential changes,however,It is still necessary to improve the filling process.The results show that the 7 coal 9 coal effect of the surface subsidence control and the non repeated mining conditions of the two layers of coal seam in the goaf under the long wall face.In the control of the same injection production ratio,non repeated mining under the conditions of coal seam overlying surface rock grouting after isolation of maximum subsidence value is 345 mm,and 2 in the presence of the overlying coal seam goaf of repeated mining conditions,then strata grouting backfill mining isolation,surface the maximum subsidence increased to 418 mm,while the sinking of a certain increase,but compared with non repeated mining conditions did not change significantly,namely the implementation of overburden isolation grouting filling difficulty does not appear essential changes,It is still necessary to improve the filling process.The measurement in site shows that the maximum subsidence is only 266 mm in II923 working face of Linhuan Coal Mine without 7# layer with grouting backfill into isolated areas.The maximum subsidence of II1021 working face is only 300 mm which is under the process of grouting backfill into isolated areas.Both experimental data in the lab and on the site show that it feasible to fulfill the target of non-village-relocation by design reasonable drills,backfill pressure,cut width even under the situation of repeated coal-mining.