Study On The Effect Of Anchor Structure And Bearing Capacity In Rock Mass After Peak

Due to the development of rock joint surface,its overall mechanical properties in surrounding rock have changed significantly.Bolt support technology has been widely concerned by engineers and technicians because of its safety,reliability,economy and practicality,which provides great guarantee for the safety and stability of surrounding rock.However,there is still a lack of systematic research on its post-peak structure.Therefore,in this thesis,numerical simulation and theoretical analysis are used to analyze its anchorage system.The deformation,failure and instability characteristics of surrounding rock after peak are summarized,and the reasons for the failure of surrounding rock are analyzed against the background of pedestrians descending from the East nine mining area of Xuzhuang Mine,and the mechanism of surrounding rock instability in roadway is revealed.According to the deformation and damage of pedestrians going down the mountain,a restoration and treatment plan is given,and it is verified by mine pressure observation,and the main conclusions are as follows:(1)With the increase of anchor density,the change of its first peak value shows that it starts from slow growth stage to rapid growth stage and then slowly grows and tends to be stable.The results show that if the supporting density is too low or too high,the stress peak effect of anchor agent will be reduced,that is,there is a suitable supporting density.In this case,the role of anchor support is obvious and economical.Secondary peak strength(i.e.maximum bearing strength after peak): When the anchor density increases,there is an approximate nonlinear relationship between the maximum load and the maximum load.At the same time,the bearing capacity of different anchor densities and without anchor in these two cases is compared,and it is found that the effect of anchor on post-peak is much greater than that before peak.(2)According to the stress and failure characteristics of the roof,under horizontal load,the main function of the anchor support method is to convert the buckling instability of single-layer rock and soil mass into overall shear,which leads to the shear failure of the whole rock and soil mass after the peak;When the overall shear failure of the anchor structure occurs,its stability depends on its softening after the peak and the thickness of the shear fracture zone.Under vertical load,the deformation of rock after peak is mainly bending instability,while the anchor cable support is to control the shear slip of bedding plane,so that the damaged layered rock and soil bodies can be combined to form a larger anchor beam-arch,thus greatly increasing its ultimate bearing capacity.(3)Support resistance increases with the increase of support length and support distance;After increasing the pre-tightening force,the active support strength of the free section peak rock will only increase;With the increase of anchor length,the active support strength of free-end peak rock gradually decreases,while the passive support strength of anchor section gradually increases;In order to make the best use of the supporting potential of the anchor and give full play to the bearing capacity of the anchor,the anchor density and the length of the anchor can be increased,and the full-length pre-tightening anchorage mode(end anchorage and full-length filling)can be adopted.(4)The coupling characteristics of surrounding rock deformation and stress in pedestrian downhill roadway in East nine mining area of Xuzhuang Mine are obtained.(5)The restoration and treatment scheme is put forward for pedestrians going down the mountain in East nine Mining Area of Xuzhuang Mine.The observation of ground pressure shows that the supporting structure is still reliable,which effectively controls the deformation of roadway rock mass under the influence of mining.