The Study On The Width And Stability Of Coal Pillar For Roadway Along Goal In Mining Of Extra Thick Coal Seam

The space of single mining in thick coal seam is large,the scope of impact of mining is wider,the mine pressure appears to have the prominent characteristic law,a new subject is put forward for the control theory of stope and roadway surrounding rock.The setting of coal pillars in fully mechanized top coal caving mining for special thick seams is an important part of the theory and technology of mine pressure control.The width of the coal pillar is too large to increase the loss of resources and excavation work,if it is too small will increase the difficulty of controlling the mine pressure and even affect normal production.In this paper,theoretical analysis and numerical simulation methods are used to determine the reasonable width and stability control of coal pillar in roadway driving along the fully mechanized top-coal caving face in special thick coal seams.The main research contents include:(1)The distribution characteristics of overlying strata are studied by using the critical layer theory.The low gravel-bearing coarse sandstone near the coal seam is a hard rock layer,which directly top is thinner,and fails to fill the goaf when it falls behind,so the overhanging beam structure is formed at the coal wall after the hard rock is broken,and the far fault block collapses.Because of its distance from the coal seam,the grit-bearing coarse sandstone in the higher level is backward to fill the goaf,and the masonry beam structure will be formed after breaking.(2)The paper analyses support pressure distribution of the goaf lateral in numerical simulation method,at the condition that this paper studies the peak distance of lateral support pressure is about 23 m at the edge of goaf,the lower stress area is about 14 m,coal pillar and the roadway will be located in the lower stress area and to avoid the peak force when the width of coal pillar is 9m.(3)The limit equilibrium theory was used to calculate the plastic zone width that produced in the adjacent coal after the upper working face is mined and the plastic zone width which generated after the tunnel excavation.The plastic zone are 4.3m and 1.72 m.The width of the middle stability zone of the coal pillar must be equal to 30% to 50% of the width of the plastic zone,the calculated range of bearing area is 1.86 ~ 3.01 m.Considering the action and stability of coal pillar,the width of coal pillar is determined to be 9 m.(4)The influence of the width of coal pillar,the thickness of coal seam,the depth of coal seam,the cohesion of coal seam and the strength of roof to the ultimate bearing zone of coal pillar is studied by orthogonal test,and the scheme that is designed to carry out by numerical simulation has 16 species.The vertical stress distribution of coal pillar in each scheme is analyzed.It is concluded that the vertical stress at the edge of the coal pillar is lower and the vertical stress in the middle part of the coal pillar is larger in the coal pillar,the overall performance is a single peak that rises first and then decreases,and based on the fact that the width of the maximum stress of the coal pillar is the width of the ultimate bearing zone of the coal pillar,the ratio of the ultimate bearing zone of the pillar is calculated,On this basis,the results are analyzed with extreme difference and the concluded is that the significance of the ratio of coal pillar to the ultimate bearing area is the width of coal pillar,the cohesion of coal seam,the thickness of coal seam,the depth of the coal seam and the strength of the roof.At the same time,the relationship between each factor and the ratio of the ultimate bearing zone of coal pillar is fitted.The correlation coefficient of the fitting formula is greater than 0.9,it is show that the factors have a good correlation with the ratio of the ultimate bearing area of coal pillar.The ratio of ultimate bearing zone of coal pillar can be estimated by fitting formula under different conditions.(5)The multiple regression analysis of the ratio of the ultimate bearing area of coal pillar to the width of coal pillar,the depth of coal seam,the thickness of coal seam,the cohesion of coal seam and the strength of roof is carried out by using MATLAB software,and the regression formula of the ultimate bearing area of coal pillar is obtained.the correlation coefficient is 0.9153,which is greater than 0.9,and the correlation is good.The formula can be used to estimate the ratio of the ultimate bearing area of coal pillar under the combined action of different factors.Based on the formula obtained,it is verified that when the width of coal pillar is 9m,the ratio of the ultimate bearing zone of coal pillar is about 23% and the width of the ultimate bearing zone is about 2.07 m.The pillar has certain bearing capacity and can maintain stability.(6)In view of the characteristic that the surrounding rock fissure of coal seam roadway is extremely developed and broken,Combined with the engineering background,and according to the theory of thick anchor plate and composite beam,the bolt and cable are selected for supporting design,the anchor parameters are obtained.The support mode is determined and the numerical simulation analysis is carried out.the extent of the plastic zone and the horizontal displacement value of the coal pillar under unsupported and supported conditions were compared and analyzed.the extent of the plastic zone is small,the horizontal displacement of value the coal pillar is about 100-200 mm,and the supporting effect is good,which can ensure normal production.