Pillarless mining technology of fully-mechanized top coal caving mining face with retained gateways along goaf

in order to have the surounding rock movement law of the retained gateway along goa in the ful-mechanized top coal caving mining face.based onN0.4311fully- mechanized top coal caving mining face of Chengzhuang Mine as a study object a new igh water quick seting materal was developed and along dstan.e grout transportation system was established.A theoretcal analysis method was appied to determine the key parameters of backil mass .With the steousev ation andunderstanding of the surounding rock movement law of the retained gatew ay along the gcafowith the high srengh bot and anchor support fechnology appiedto the eained gateway,the reinforce bar laders set in the bacill tags could control the deformation of the retained gateway and the backll mss The study resuts showed tat the roof ressure of the retained gateway was reached to the peak value at 5 ~ 4D m behind the cal mining face.At the 150 m behind the coal minin fae.the pressure was rapily reduced,was fially stablized at 30』 m behind the coal minin face and was 7 MPa.The internal pressure of the backill mass would be ste dily inreased with the distance to the coal mining faceincreased.At the about 10 m behind the coal miming face.the pressure would be varied.NWhen the cal mining faceput forward with 80 m,the stress would be stabilized and finally the relevant stress within the backill mass would not be over 4 MPa.