| With the increase of mining depth,the complex geomechanics environment of deep gob-side entry retaining makes the surrounding rock failure characteristics and control technology significantly different from that of shallow gob-side entry retaining,especially the deep backfilling retaining roadway(backfilling retaining roadway in working face).In recent years,the problem of surrounding rock control in deep backfilling retaining roadway has been the focus of attention and research by mining scientists and rock mechanics workers.According to plastic mechanics,the stress of surrounding rock is the superposition of deviatoric stress and spherical stress.The interaction of maximum principal stress,intermediate principal stress and minimum principal stress is taken into account in both deviatoric stress and spherical stress,which can scientifically reveal the relationship between stress evolution of surrounding rock and deformation and failure of surrounding rock in deep retaining roadway.Therefore,using deviatoric stress and spherical stress to analyze the stress state of rock mass,the surrounding rock control technology of deep backfilling retaining roadway proposed by deviatoric stress,spherical stress and plastic zone is more scientific and comprehensive than that proposed by traditional methods.This paper takes 1126 deep backfilling retaining roadway in Xingdong Coal Mine as engineering background,by means of laboratory test,numerical simulation(based on the strain softening constitutive model),theoretical modeling analysis,field engineering test and other research methods to research the physical and mechanical properties of backfilling body used in deep backfilling working face of Xingdong Mine,spatio-temporal evolution and influencing factors of deviatoric stress,spherical stress and plastic zone of surrounding rock in deep backfilling retaining roadway,spatial position relationship of deviatoric stress,spherical stress and plastic zone in surrounding rock of backfilling retaining roadway and surrounding rock control principle and method of deep backfilling retaining roadway.Then,the system of "three-in-one+asymmetric support" of surrounding rock of deep backfilling retaining roadway is put forward,and the mechanical model of asymmetric support structure of surrounding rock of deep backfilling retaining roadway is established.The specific parameters of asymmetric support of surrounding rock in deep backfilling retaining roadway are determined,and the principle and method of coordinated control of surrounding rock in deep backfilling retaining roadway is formed.The results obtained are applied to field engineering practice.The main results and conclusions were as follows:(1)Physical and mechanical tests of filling materials in deep backfilling working face:The backfilling body C2(water cement ratio 5:1)is more suitable for the complex mechanical environment of deep mine than backfilling body C1(water cement ratio 6:1).The backfilling body with lateral pressure has higher residual strength and good bearing capacity than the backfilling body without lateral pressure.Therefore,the application of protective surface components on the empty side of backfilling body can significantly improve the bearing capacity of shallow backfilling body,so as to meet the support requirements of asymmetric large deformation of surrounding rock in deep backfilling retaining roadway.(2)Spatio-temporal evolution law of surrounding rock deviatoric stress and plastic zone in deep backfilling retaining roadway and its influencing factors effect:? Distribution regularity of axial deviatoric stress and plastic zone along roadway shows the more obvious influence zone of the advanced mining about is 32 m on the roof,but about 16 m on floor and two ribs.The more obvious influence range of the lag mining about is 32 m on the roof,but about 24 m on floor.The solid coal side and backfilling body side are always affected by the lag mining.? With the advancing of working face,the time-space evolution of deviatoric stress of surrounding rock in deep backfilling retaining roadway is thin elliptical shape,approximate circle shape,small semicircle arch,large semicircle arch,and fantail arch.The peak value zone of deviatoric stress is transferred from the roof-to-floor to the corner of roof and floor in solid coal side and the solid coal side.Meanwhile,the order of plastic zone evolution state of the surrounding rock of the gob-side entry retaining as follow:approximate elliptical shape,approximate circle shape,hemisphere shape.Both deviatoric stress and plastic zone of surrounding rock in backfilling retaining roadway have asymmetric distribution,and the outline of plastic zone is located in the peak value zone of deviatoric stress with a spacing of 0-2 m,the peak value zone of deviatoric stress is located in the elastic-plastic interface zone.Accordingly,it is considered that the side of backfilling body in goaf needs to be strengthened with emphasis,the roof needs to be strengthened asymmetrically,and the corner of roof and floor,and the solid coal side need to control the stability of unstable rock mass within the peak value zone of deviatoric stress.At the same time,under different influencing factors,the peak value zone of deviatoric stress is located in the elastic-plastic interface area,the expansion angle of the peak deviator stress zone is in nonlinear proportional to the plastic zone,and the main and secondary order of the spatio-temporal evolution factors of deviatoric stress are:filling height>mining depth>lateral pressure coefficient>mining height.(3)Spatio-temporal evolution law of surrounding rock spherical stress in deep backfilling retaining roadway and its influencing factors effect:With the advancing of working face,the peak value of spherical stress in surrounding rock of deep backfilling roadway gradually shifts from roof and floor to solid coal side,and the distribution of spherical stress gradually evolves from petal shape to hyperbolic shape divided by spherical stress transition zone.In the gob-side entry retaining section,the outline of plastic zone of roof and floor is located in the interior of spherical stress transition zone of roof and floor,and the spacing is 1-2 m.The outline of plastic zone of solid coal side is located in the interior of the peak position of spherical stress of solid coal side,and the spacing is 0.2-0.6 m.Therefore,the transition zone of spherical stress is located in the elastic-plastic interface region.The transition zone of spherical stress has "skeleton supporting effect" on the undamaged rock mass in the surrounding rock of retaining roadway,and then"protective effect" on the surrounding rock of retaining roadway.At the same time,under different influencing factors,the spherical stress transition zone is located in the elastic-plastic interface area,which plays a "protective role" to the surrounding rock of retaining roadway,and the main and secondary order of the spatio-temporal evolution factors of spherical stress are:filling height>mining depth>lateral pressure coefficient>mining height.(4)Based on the spatio-temporal evolution law of deviatoric stress,spherical stress and plastic zone in surrounding rock of the deep backfilling retaining roadway and their spatio-temporal relationship,the "three-in-one" spatial position relationship of peak zone of deviatoric stress,transition zone of spherical stress and outline of plastic zone is obtained,and the system of "three-in-one+asymmetric support" is put forward.The structural mechanics model of the composite beam which is consist of the roof truss anchor cable,the steel-concrete bracket and the single hydraulic prop is established,and the stability of steel-concrete bracket beside roadway is analyzed.The critical pressure of steel-concrete bracket under different constraints is obtained,and the safeguard measures to realize its stability are put forward.Finally,the asymmetric support parameters of surrounding rock in deep backfilling retaining roadway are determined.(5)The principle and method of "three-part,three-pass,three-cover,four-in-one and five-in-one" for synergistic control of surrounding rock in deep backfilling retaining roadway has been formed and applied in the No.1126 haulage roadway(retaining roadway)in Xingdong coal mine.There are no phenomena such as compression bending damage of the steel-concrete bracket and the single hydraulic prop and failure of bolt-cable support.It is shown that the surrounding rock deformation of gob-side entry was effectively controlled. |
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