Study On The Theory And Technology Of Anchor Cable With C-shaped Tube Structure Support In Deep Roadway

When the roadway is dug through several rock layers,the thickness of the rock layers is uneven and the mechanical properties differ greatly,and the rock layers are prone to separation and inter-layer misalignment,and the roadway deformation reflects uneven and non-symmetrical phenomena under the action of soft rock,rock dip and high ground stress.Conventional support members are affected by shear strength and are easily broken by the lateral shear force generated by interlayer misalignment and shear expansion.Therefore,an effective support method is necessary to meet the demand for high preload and high shear resistance of the support elements in the through-layered roadway.Anchor cable with C-shaped tube(ACC)provides a high shear strength support element in the free section while applying high preload.In this thesis,on the background of high horizontal stress inclined rock layer crossing roadway,the deformation and failure mechanism of inclined rock layer crossing roadway and the key influencing factors are systematically studied by field test,indoor test,numerical simulation and theoretical analysis for the demand of asymmetric deformation of roadway,lateral action of interlayer misalignment to the support members,high preload of deep roadway demand on the support members.The difference of shear performance of ACC,rock bolts,and cable bolts under various conditions,and the influence of key parameters on the shear performance of ACC were investigated by double shear test without friction at the joints,and the shear process of ACC was initially analyzed based on super-stationary beam theory.The design method of ACC support was proposed by combining the characteristics of ACC shear performance and the deformation and failure mechanism of through-layer roadway,and industrial tests and field monitoring were conducted.The main findings are summarized as follows:(1)Analysis of failure mechanism and influencing factors of deformation in through-layer roadway.The deformation of the roadway varies greatly when the coal seams are located in different positions of the roadway,and the deformation is affected by the rock dip angle and horizontal stress to show obvious unevenness.When the coal seam is located on the roof,the deformation is mainly vertical displacement,and the intersection of the coal and rock layers on the roof is a potential slip zone,where the support members are subjected to higher tensile load and lateral shear load at the same time.When the coal seam is located in the wall,the deformation is mainly horizontal displacement,and the support members that pass through the coal seam and sandy mudstone layer at the same time in the wall will be subject to large tensile and shear loads,which requires high shear resistance of the support members.When the coal seam is located at the floor,the overall deformation of the roadway is mainly bottom dropsy,the horizontal displacement gap of the coal and rock layers at the angles is large,and the support members here will bear a large shear load.The horizontal stress mainly affects the non-uniform deformation and the relative displacement of the potential slip zone of the roof,but has no effect on the distribution of the slip zone.The rock dip angle not only affects the non-uniform deformation of the roadway and the relative displacement of the potential slip zone,but also affects the distribution of the slip zone,with the increase of the dip angle of the rock layer,the slip zone is moved towards the low wall.(2)The shear performance tests of rock bolts,cable bolts,and ACC.The results of the tensile tests and the double shear tests under frictionless at joints showed that the rock bolts were failed by tensile bending after shearing when the surrounding rock strength was less than 50 MPa.Increasing the preload and the surrounding rock strength will reduce the shear displacement.The joint peak shear strength of rock bolt is positively correlated with the surrounding rock strength when the preload is less than100 k N,and the joint peak shear strength is negatively correlated with the surrounding rock strength when the preload is more than 100 k N.Cable bolts in the surrounding rock strength less than 50 MPa after shear failure are tensile shear failure,but more inclined to tensile failure.The preload force indirectly affects the shear displacement and the shear strength of the joint at failure by influencing the elastic-plastic state of the cable bolt.The peak shear strength of cable bolt at the joints is negatively correlated with the preload,and positively correlated with the surrounding rock strength and cable bolt diameter.The shear displacement is negatively correlated with the preload and surrounding rock strength,and positively correlated with the cable bolt diameter.The failure of cable bolt in ACC after shearing when the surrounding rock strength is less than 50 MPa is due to tensile shear failure,but more inclined to tensile failure.The shear strength of ACC joint is negatively correlated with preload,and positively correlated with cable bolt diameter.The shear displacement is negatively correlated with preload and surrounding rock strength,and positively correlated with cable bolt diameter.ACC has stable shear resistance in different strength surrounding rocks and shows the best shear resistance in medium-hard rocks.(3)Study on the key parameters of ACC.The results of the double shear tests shows that the percentage increase of ACC shear strength increases exponentially as the thickness of the C-shaped tube increases.The cross-sectional shape of the tube is C-shaped or O-shaped has no significant effect on the shear resistance of ACC.When the end of the C-shaped tube reaches the joints,the shear strength of ACC is the same as ordinary cable bolt,and it is at least 15 cm beyond the joints to play the shear performance properly.There is a balance interval for matching the strength of C-shaped tube and cable bolt.Too low strength of C-shaped tube will fail the ACC structure by fracturing prematurely and significantly reduce the shear displacement,and too high strength of C-shaped tube will cause the waste of C-shaped tube strength,which is limited by the tensile performance of cable bolt.(4)Comparison of shear performance of rock bolts,cable bolts and ACC.The average shear strength of ACC is 1.8 times that of rock bolts and 1.3 times that of cable bolts for different rock strengths according to the actual preload of the project.The standardized shear strength contribution of cable bolts is reduced by increasing the preload when the braiding form is the same,while the diameter has no effect.1×19cable bolts provide 10.5% higher standardized shear strength contribution than 1×7.Increasing the preload can reduce the shear force on the cable bolts,but will reduce the shear displacement and shear strength,which is the reason why cable bolts cannot combine high preload and high shear resistance.Cable bolt in ACC bear lower shear force than normal cable bolt,and have higher shear strength and shear displacement,which can apply high preload and have high shear resistance at the same time.The shear strength of ACC is 140.8% of that of full anchor rock bolt and 87.9% of that of full cable bolt,and the shear resistance of ACC can exceed that of full anchor rock bolt and cable bolt after choosing reasonable parameters.(5)Analysis of the ACC shear mechanical model.Based on the super-stationary beam theory,a theoretical analysis of the shearing process of ACC was carried out,and the relationship between the axial force,shear force,surrounding rock reaction force and shear displacement of ACC during the shearing process was initially discussed.The model can predict the axial and shear force on the cable bolt and C-shaped tube,the deflection angle,and the shear strength of the joint bolted by ACC when ACC fails based on the parameters of cable bolt,C-shaped tube,and surrounding rock.The calculated results are more consistent with the test results.The analysis results show that the axial force on the cable bolts in ACC is proportional to the square of the shear force;when the surrounding rock is in the elastic and plastic deformation stage,the shear force on the cable bolt at the intersection of ACC and the joint is 1.40 times and9.57 times of that on the C-shaped tube,respectively,and the shear resistance of the C-shaped tube is mainly reflected in the elastic deformation stage of the surrounding rock;when the materials of the cable bolt and the C-shaped tube are the same,the ultimate surrounding rock reaction force on the cable bolt is 2.37 times of that on the C-shaped tube.(6)ACC support design method and engineering application research.Based on the test conclusion and the failure mechanism of the through-layered roadway,the ACC support mechanism was elucidated,and the ACC support design and parameter selection method applicable to the through-layered roadway was proposed and applied in the field in the tape tunnel of Zhengling Mine.The monitoring results showed that ACC can effectively cope with the tensile and shear loads of the through-layered roadway,and the extruded arch composed of steel mesh,concrete spraying layer,and ACC can effectively control the stability of the through-layered roadway.