Research On Floor Heave Control Technology Of Gob Side Entry Retaining By Roof Cutting And Pressure Relief In Selian 2 Coal Mine

The unique roadway forming method of gob side entry retaining technology with roof cutting and pressure relief can not only improve the recovery rate of coal seam in working face and improve the ventilation environment of working face,but also relieve the continuous tension of working face to the greatest extent without manual masonry of filling wall beside the roadway.The improvement of gob side entry retaining technology system with roof cutting and pressure relief is of great significance to the realization of safe and efficient mining of underground coal resources in China and It is of great practical significance to change the stage.Roof cutting and pressure relief gob side entry retaining is usually implemented in the existing roadways,and most of them are mining roadways.In engineering practice,the floor of roof cutting and pressure relief gob side entry retaining is still inevitably faced with floor heave.Floor heave is not only related to the success or failure of gob side entry retaining,but also related to the safety and efficiency of coal mining in two adjacent working faces.Therefore,how to control the roof cutting and pressure relief along the gob side entry retaining floor heave of gob retained roadway is an urgent problem to be solved for safe and efficient production in China.Based on the engineering background of 12412 working face in selian 2 coal mine,this paper studies the floor heave law and the key factors affecting the floor heave of the return air channel in the process of roof cutting and pressure relief gob side entry retaining by using the method of numerical simulation and theoretical analysis after the field investigation.On the basis of the above theoretical research,some measures are taken to solve the floor heave problem of the return air channel.The technical scheme of grouting reinforcement for deep and shallow holes in the bottom plate is proposed,and the field industrial test is carried out in the section of 1650～2000m,the theoretical research and industrial test show that:(1)The direct cause of floor heave in the process of gob side entry retaining with roof cutting and pressure relief is the mine pressure behavior of 12412 working face after mining.The fundamental reason is that the floor has not taken any support and reinforcement measures,and the mechanical properties of surrounding rock in the plastic zone of the floor have been continuously deteriorated under the influence of mining dynamic pressure and rock burst,which further leads to the bearing strength of the floor surrounding rock persistent decrease;(2)To some extent,the anchor beam mesh cable supporting structure on the side of the return air channel and the top can improve the stress environment of the floor and reduce the floor heave,but it can not prevent the floor heave damage fundamentally,and the floor heave control must take targeted measures;(3)The numerical simulation results show that the floor heave decreases from 344.06mm to 99.52mm when the cohesion of the surrounding rock in the plastic zone of the floor increases from 0.5MPa to 0.8MPa,with a decrease of 71.07%;(4)The floor grouting can effectively enhance the integrity and residual bearing strength of the broken surrounding rock of the floor.After the implementation of the deep and shallow hole grouting reinforcement technology,the floor heave of the return air channel in the industrial test section after the mine pressure behavior is stable between 105～135mm,far less than the floor heave of 600～800mm in the nongrouting section,and the floor heave of the return air channel in the test section after the floor grouting is in the mine during the pressure behavior,the good flatness was maintained,and there was no floor heave damage.Based on a specific engineering example,this study studies the floor heave mechanism in the process of gob side entry retaining with roof cutting and pressure relief,puts forward the corresponding floor heave control ideas,formulates the floor heave control technical scheme and carries out the field industrial test,and achieves the expected floor heave control effect,which has a certain reference value for the floor heave control of gob side entry retaining with roof cutting and pressure relief.Figure 46 table 15 reference 82...