Research On The Stability Of Surrounding Rock During Working Face Mining

The increase of mining depth of colliery,which is with the purpose of meeting the increasing demands of coal brings about a series problems such as roadway support of soft rock and the pressure bump of tully mechanized coal face.Thus,it is necessary to further the calculation of the pressure bump of fully mechanized coal face and the supporting research on soft-rock roadway.This text discusses the first weighting of some fully-mechanized working face and the intervals of periodic weighting and recognizes the levels of danger of pressure bump at the very beginning on the basis of field monitoring and the technology of numerical simulation;and three-dimensional model is further established according to the general situation of fully-mechanized working face and the relations between surrounding rock stress in goaf and the displacement changing as the advanced distance changes are analyzed;at last,the analyses of how the shift of surrounding rock stress of fblly mechanized coal face affecting rail lane are being conducted and the numerical simulation of the bolting structure is under way.Main conclusions are summarized as following:1.The interval and period of first weighting ot 21141 working face are calculated to be 36m and 11m respectively by means of theories,among which the location of the main roof conforms to the danger segment when the first pressure bump happened during the field monitoring.2.The danger segments of fully-mechanized working face when pressure bump happened are:36m.130m,270m and 400m away from the open-off cut,especially the first main roof pressure overlapped the location of the first danger segment of pressure bump;moreover that of main roof releases large amount of energy.It is suggested that the long wall of coal rake should be rejected water and hole should be drilled for pressure relief,helping lower the incidence rate of pressure bump.3.As the 21141 working face pushes forward,shearing stress on selected path should be increased on average as the change of advanced distance.In particular,when the advance distance of working face narrows to be less than 450m,the shearing stress on every path goes up,indicating that the surrounding rock stress of coal mining face goaf is intensified so that rock burst occurs easily;on contrary,when the advanced distance surpasses 450m,the increasing trend of shearing stress is not obvious,showing that the rock mass near the working face tends to be stable4.Affected by 21121 exiting goaf,when 21141 working face moves forward,the surrounding rock stress field and displacement field amplify apparently;the biggest Mises and the biggest displaced are both located within the surrounding rock in goaf,which reflects that the fully-mechanized coal face has a great impact.5.Influenced by the minging of two adjacent working face,the transformation of surrounding rocks in main roadways and the change of stress are prominent:when the bolt length is 2m,the location where the shear stress of surrounding rocks concentrate on is about 2.2m away from the roadway wall and the anchorage section is placed in the high stress concentrated area.It is advised that the bolt length should be increased to 3m for the sake of the security of supporting structure.Figure 22 table 4 reference 54...