Study on Surface Ground Movement Law of Coal Rejects Backfill Mining Under Thick and Loose Overburden Strata

In order to analyze the surface ground movement law of coal rejects backfill mining under thick and loose overburden strata,the FLAC3D numerical simul ation software with orthogonal and uniform designed test to calibrate the mechanics parameters of indoor rock samples was applied to individually establish and calcula te numerical model of the coal rejects backfill mining under the different thickness of the thick and loose overburden strata. Under the conditions of the same base rock t hickness and different loose strata thickness and under the conditions of same mining depth and different loose strata thickness,the study on the surface ground move ment law of the coal rejects backfill mining showed that,firstly,under the conditions of the same base rock thickness ,with the loose strata thickness increased,the max s ubsidence value of the surface ground above the coal rejects backfill mining,the max horizontal movement value and the tangent value of main effect angle would be in creased.Secondly,the surface ground subsidence coefficient of the backfill mining under the thick and loose overburden strata would be increased in linear with the rate of the loose strata thickness and the mining depth.Finally,the mining depth would be the major factor affected to the surface ground movement scope of the coal rejects backfill mining under the thick and loose overburden strata and the thick and loose overburden strata would be less affected to the surface ground movement scope.