Rational Anchoring Parameter Analysis Of Coal Rock Bolt Supporting In The Upper Part Of Deep Coal Roadway

As the coal mining develops gradually towards the deep,the breaking and deformation analysis of deep soft coal and proper supporting issue have become particularly important.In order to select proper support and its arrangement,the combination of site test and numerical simulation is adopted.Firstly,main factors(primary rock stress,roadway section size and coal lithology)affecting deep soft coal breaking and deformation are determined through theoretical analysis and then values of physical mechanics parameters of coal are measured with relevant test(elastic modulus,Poisson ratio,cohesive force and inner friction angle).Reasonable FLAC3 D numerical calculation model is built.Secondly,the fitting equation is obtained with the numerical simulation results,the displacement values in each direction obtained from Tecplot post-processing software and by fitting of displacement with software Origin.The displacement gradient functions of different supporting time and the different pre-stress values in the surrounding rock are obtained by taking the derivative of the fitted curves.The displacement gradient function can reflect the degree of fragmentation and its distribution law in different positions of rock mass after excavation and unloading or supporting.The results show that: 1)In different directions of the roadway,the deep rock mass of the roadway is greatly affected by the prestress of the anchor cable;with the increase of the prestress in the anchor cable,the degree of breakage and expansion will be significantly reduced.2)In different directions in the roadway,the shallow rock mass of the roadway is obviously affected by the prestress of the anchor cable;for the surrounding rock near the anchor cable,that is,within the effective range of the anchor cable prestress,the application of appropriate prestressing force can help to reduce the degree of breakage of this part;for the surrounding rock far from the anchor cable,the application of prestress will only aggravate the breakage of surrounding rock.3)Excessive prestressing will only produce side effects on the stability of the rock mass on the roadway surface.For example,when the prestress reaches 300 KN,the surface expansion of the surrounding rock is intensified and the maximum total displacement is significantly increased.