Study On Pressure Relief Mechanism And Engineering Application Of Sectional Boreholes Enlargement Technology

With the increase of frequency,intensity and damage degree of rock burst occurrence in coal mine,large diameter boreholes technology for prevention and pressure relief of rock burst has become an important control method of mine rock burst disasters due to its low disturbance,fast construction,easy operation and high safety.In the process of prevention and control of rock burst disaster in coal mine,the research on how to relieve pressure by boreholes technology in the dangerous area without destroying the overall strength of roadway surrounding rock is inadequate,and the conventional large diameter boreholes technology is contradictory to the control of surrounding rock.Therefore,based on field investigation,laboratory test,numerical simulation,theoretical analysis and other methods,this paper puts forward the technology of pressure relief by piecewise enlargement boreholes on the basis of analyzing the contradiction between pressure relief of conventional large diameter boreholes and roadway surrounding rock control.The mechanism of pressure relief of piecewise enlargement boreholes,the deformation law of roadway of pressure relief by piecewise enlargement boreholest and the energy release of surrounding rock are deeply studied.The field practice verifies the effect of pressure relief and rock burst control.The main contents and achievements of this paper are as follows:(1)The case of influence of roadway stability of pressure relief by conventional large diameter boreholes on haulage roadway in 6307 working face of Tangkou coal mine is analyzed in depth.The deformation characteristics of roadway surrounding rock in the area of pressure relief by conventional large diameter boreholes on haulage roadway in 6307 working face are studied.Through numerical simulation,the influence of boreholes diameter,boreholes depth and drilling spacing on the effect of rock burst control and pressure relief and roadway stability is obtained.In addition,the contradiction between the pressure relief of conventional large diameter boreholes and the surrounding rock control of roadways is analyzed,which provides a basis for the construction of the pressure relief method of piecewise enlargement boreholes.(2)Uniaxial loading tests were carried out on gypsum materials with three different parameter schemes,diameter,depth and spacing of boreholes,and the strength and failure characteristics of materials with three different parameter schemes were obtained.Based on the results of numerical simulation,the mechanism of pressure relief by piecewise enlargement boreholes is analyzed,the macro and micro characteristics of failure of piecewise enlargement boreholes specimens are studied,and the principle of pressure relief by piecewise enlargement boreholes is revealed,which provides a theoretical basis for the implementation of pressure relief technology by piecewise enlargement boreholes in roadways.(3)According to the actual situation of haulage roadway in 6307 working face,the numerical simulation test was carried out on pressure relief by piecewise enlargement boreholes technology of different boreholes enlargement diameter,boreholes enlargement depth and boreholes spacing.The coal energy around the roadway under different parameters and deformation characteristics of roadway deformation were obtained.The energy release and deformation law of roadway deformation during the process of pressure relief by piecewise enlargement boreholes are studied.The effects of boreholes enlargement diameter,boreholes enlargement depth and boreholes enlargement spacing on coal energy dissipation and roadway stability around the roadway are analyzed.The boreholes layout parameters of haulage roadway in 7307 working face of relief by piecewise enlargement boreholes were determined.(4)Based on the numerical simulation,the boreholes layout parameters of haulage roadway in 6307 of pressure relief by piecewise enlargement boreholes are given,and relief by piecewise enlargement boreholes technology is carried out in field engineering application of haulage roadway of the 6307 working face of Tangkou Coal Mine.The rock burst pressure monitoring and deformation observation were carried out on the site.The results show that after using pressure relief by piecewise enlargement boreholes technology scheme,the accumulation of coal energy is reduced,and the effect of rock burst control is obvious.At the same time,the deformation and failure of the surrounding rock of the roadway has been effectively controlled,and the construction efficiency of using the pressure relief by piecewise enlargement boreholes is 1.5 times higher than that of the conventional large diameter boreholes.