Study On Support Technology Of Right Angle Trapezoidal Roadway In Slowly Inclined Soft Coal Seam

The coal seam in Shi Tan Jing No.2 Coal Mine has a dip angle of 21°to 27°,a burial depth of 449 to 520m,an average thickness of 5.6m,and a compressive strength of about 10MPa.The roadway is excavated along the roof of the coal seam,and the cross-section is in the form of right-angle trapezoid.The roadway is supported by anchor net,and the roadway has severe asymmetric damage or even collapse,which directly affects the safety and benefit of coal mine production.Based on this engineering background,this paper uses theoretical analysis,numerical simulation,indoor similarity model test and on-site monitoring to carry out research on this kind of roadway support technology.The main work and conclusions are as follows.(1)Through field investigation and theoretical analysis,it can be seen that the main reason for the serious asymmetric destruction and even collapse of the roadway is the obvious asymmetric property of the stress distribution of the surrounding rock of the roadway due to the inclination of the coal seam.The indoor similar model test results further show that:the stress concentration of the roof is inclined to the low top,the low-stress concentration of the roadway is significantly larger than the high top,and it is more obvious with the increase of the ground stress.Under the action of this asymmetric stress,the deformation of the low-top is significantly greater than that of the high-top,which also causes the bottom plate to exhibit asymmetrical uplift failure characteristics.(2)Based on the analysis of support theory,according to the stress-deformation asymmetric characteristics of the surrounding rock of the right-angled trapezoid tunnel in gently inclined soft coal seam,two design principles of support parameters are proposed.The supporting parameters were designed.(3)The numerical calculation model is used to compare and analyze the stress distribution and deformation law of the tunnel before and after it is supported.The results show that after the roadway is supported,the vertical and horizontal asymmetric stress distribution characteristics of the surrounding rock of the roadway are significantly improved,the vertical stress is obviously transferred to the middle of the roadway,and the difference in the stress concentration of the surrounding rock is reduced.The overall deformation of the tunnel tends to be stable.It shows that this support scheme can effectively control the stability of surrounding rock.(4)The on-site monitoring results show that:the amount of roof sinking,the convergence of the two sides,the separation of the roof,and the stress of the anchor are all within the allowable range.It further shows that the support scheme is scientific and reasonable,and also provides scientific basis and reference for the support of gently inclined soft coal roadway in similar areas.