Study On The Layout Of The Last Drilling Holes Of Grouting Backfill Into Isolated Areas Within Overburden For Mining Under Villages On Open-off Cut

Mining under Villages on open-off cut refers that the village on the ground and other construction building only cover some block of coal face on the open-off cut side, it belongs to the partial coal of holding down issues. Grouting backfill into isolated areas within overburden is the method of using both grouting backfill and isolated coal pillar to control key stratum and the surface subsidence. For the grouting backfill into Isolated Areas, the position of the last drilling group often has some contradiction, that is, the filling area is too small to guarantee the quality of the project, or the filling area is too large to cause irrationality of economic. Therefore, the position of the last drilling group should be obtained under the precondition of satisfying engineering requirement and rationality of economic cost control. Research methods such as theoretical analysis, numerical simulation and field measurement are adopted in the paper.Theoretical study shows that the reasonable position of the last drilling group location should make sure that when the backfill play a role, the main key layer of mining area under village are without large disturbance, so as to keep the stability of overburden for mining, control the surface subsidence and protect ground village.The simulation results show that the grouting control area is larger, the surface subsidence control effect is better, for the non full mining coal area, when the filling control area is exactly equal to the pressured coal distance, the village location is the inflection point, the maximum deflection value fulfill reducing settlement rate required, the position of last drilling group should be 150m away from coal line; for the full mining area, when the filling area is exactly equal to the full mining distance, surface subsidence value is the turning point corresponding to the simulation of the village location, the village location is the inflection point, the maximum deflection value fulfill reducing settlement rate required, the position of last drilling group should be 150m away from the distance of full mining. The simulation results also show that grouting backfill conforms to the Law of diminishing the boundary effect, namely under the other conditions remain unchanged, if input grouting quantity equivalent to a continuous increase, reduce sink effect also increases; when it increases to a certain value, increased reducing sink effect is more and more low with the increase of quantity of grouting.Researches guide Huaibei 766 mining face the Layout of the last drilling holes of grouting backfill into isolated areas within overburden for mining on open-off Cut. The mining face belongs to the non full mining coal area type. Design the pressured coal distance as the control area, the end group drilling above the coal line distance is 214m. Through grouting, the maximum subsidence of ground village is 97mm. The coal is mined safely without relocation and any damage to the buildings on the ground, significant control effect of reducing subsidence is achieved.