Study On Borehole Destressing Mechanism And Yielding Support Technology In High-stress Roadway

With the continuous extension of coal resources to the deep,the mechanical properties of coal and rock have changed significantly,and the control of surrounding rock of roadway has become increasingly difficult.In addition,most deep roadways will be strongly affected by High crustal stress and mining,which will lead to further deterioration of surrounding rock stress environment.It is urgent to solve the problem of continuous large deformation of high-stress roadway.Taking the track roadway in the deep level 11 district of Dongpang Coal Mine as the object,using the methods of numerical simulation,theoretical calculation and indoor experiment,this paper studies the stress transfer of surrounding rock and the control of large deformation of roadway.Finally,the combined support technology of “pressure destressing and yielding” with reserved deformation space is put forward,which has been successfully applied in the field.The main contents of this paper are as follows:(1)According to the geological conditions and deformation characteristics of track roadway in 11 district,using numerical simulation method,the stress distribution characteristics and evolution law of surrounding rock under different disturbances are studied,and the vertical stress distribution of surrounding rock under different positions is analyzed.The influence of different disturbance and stopping mining position on the deformation of surrounding rock and the deformation law of shallow surrounding rock in different parts of roadway are studied,and the reasons leading to the failure of supporting components are discussed.(2)From the point of view of stress transfer of surrounding rock,it is proposed to use borehole destressing technology to transfer high stress around the roadway.Based on the theory of elasticity,the stress distribution around the borehole is analyzed,and the analytical formula of the distribution radius of the borehole destressing zone is deduced when the lateral pressure coefficient is not 1.Combined with theoretical analysis and field observation results,the direction and timing of destressing are determined.The reasonable range of key parameters(length,spacing,row spacing and diameter)of boreholes is determined by numerical calculation method combined with the evaluation index of pressure relief effect of boreholes(peak stress,peak stress position,vertical stress at original peak position and peak stress characteristics between adjacent holes).(3)The structural and functional characteristics of the yielding bolt system and the way to realize the yielding action are analyzed.The load-deformation curves of single yielding pipe,double yielding pipe and high-strength double yielding pipe are obtained through compression tests of different types of yield pipe.The mechanical characteristics of each stage are analyzed,and the characteristic parameters such as yielding point,maximum yielding distance and yielding stability coefficient of different types of yielding pipe are obtained.Combining with the engineering practice of the test roadway,the reasonable specification of the yielding pipe component is selected.(4)Based on the results of theoretical analysis and numerical simulation,the combined control technology of “pressure destressing and yielding” with reserved deformation space is proposed.The process flow is defined and applied to field industrial test.The deformation of surrounding rock and the axial force of bolt are monitored in the test roadway,and the law of rock pressure appearing in the track roadway and the control effect of surrounding rock are analyzed.Engineering practice shows that the combined control technology can maintain the stability of surrounding rock.