Research On Mechanism And Controltechnology Of Floor Heave In Gob-side Entryretaining Of Licun Coal Mine

In order to reveal the mechanism of the floor heave in the deep well along the goaf,according to the geological conditions of the 1301 working face of Licun Coal Mine,a mechanical model reflecting the mechanism and control of the bottom drum in the gob along the goaf was established using elastic mechanics.The horizontal stress and vertical stress in the stress field of the roadway are studied in the four stages,which is the stress release of the original rock in the goaf after the working face is advanced,the fragmentation of solid coal body and vertical stress concentration in floor rock caused by lateral support pressure of roadway solid coal body,reaction force transmitted to the floor by roadside filling body to provide support resistance and the original rock stress in coal seam.（1）It is found that the horizontal stress in the floor is much greater than the vertical stress during the the first and second mining impact periodmining in gob-side entry retaining.The vertical stress caused the bending of the roadway floor,and the horizontal stress further aggravated the bending.When the horizontal tensile stress on the roadway floor surface is greater than the direct bottom tensile load,vertical cracks are generated;when the internal shear stress on the floor is greater than the floor shear strength,the vertical cracks are penetrated by horizontal cracks.At the same time,the internal stress formula of the floor of the mining roadway was derived.The main research results are as follows:（2）Through the FLAC numerical simulation software,the influences of burial depth,stress release in the mined-out area,direct bottom concentration stress under lateral support pressure,and backfill support resistance to the floor heave were studied respectively.It was found that when the working face was pushed forward,the displacement limitation in the vertical direction of the goaf was lifted,the original rock stress was released on a large scale,and the bottom was bulged as a whole.The mining roadway is located in the boundary area of the goaf,and the bottom drum is suppressed,but the stress concentration in the floor rock layer is intensified.（3）When the roof span of the goaf is backward,the lateral key block intensifies the vertical stress concentration in the coal of the roadway,which greatly increases the vertical load in direct bottom,which causes the floor under the coal sinking on the basis of the original floor heave.The floor heave has been relatively increased.At the same time,because the coal body in the crushing area under the lateral critical block is difficult to suppress the floor heave,it is equivalent to increasing the floor heave space in the roadway section.After designing the strength and support width of the backfill body,the reaction force of the backing body support resistance to the rock formations on the bottom floor is obtained through numerical simulation.This force can inhibit the floor heave of the mining roadway,but will aggravate the stress concentration on the side of the roadway filling body.Because the width of the filling body is generally smaller than its height and smaller than the width of the mining roadway,and the support resistance of the filling body is often not higher than the vertical stress in the original rock stress field,the highest volume of the floor heave in the mining roadway is biased to the side of the coal.（4）The shape of the bolt determines that it can be well controlled to the vertical stress after it is driven into the floor or side of the roadway section,but the control effect of the horizontal stress is not good.However,horizontal stress is much greater than vertical stress.In order to better deal with the above-mentioned phenomenon,the floor heave treatment technology for cutting seams along the goaf in deep buried coal seams is proposed as a supplement to the traditional bottom clean and bolt support floor heave treatment technology.Numerical simulations of the gob-side entry retaining have found that when the working face is mining,there areτ_yxandτ_yzstress concentrations in the floor rock layer between the filling body and the ends of the lateral key block on the goaf side.And cut a slope in these two stress overlapping areas.When the horizontal stress is released,the horizontal stress is converted into a vertical stress,and finally the stress concentration and the difference between the three-way stress of the bottom rock layer along the roadway are reduced,and the stability of the bottom rock layer of the roadway is improved.