Study On Anchoring Performance And Influencing Factors Of Bolt Under Confining Pressure

Bolt support is an economical and effective means for coal mine roadway support.However,due to the influence of the soft rock,strong mining,large deformation and other characteristics of the roadway,the stress of the surrounding rock of the roadway changes,resulting in varying degrees of radial damage in the bolt radial direction.Confining pressure and changes in confining pressure directly affect the load-bearing characteristics of the bolt anchoring system.At present,the research results on the influence factors of bolt support are relatively abundant,but there are few researches on the influence factors of the confining pressure.Based on the theoretical analysis of the anchoring performance of resin bolts,this paper systematically studied the influence of confining pressure,anchoring length,bolt diameter,and surrounding rock strength on the anchoring performance of resin bolts through laboratory tests.The effect of pressure on the anchoring force of resin bolts,and the research results have important practical significance for deep mine roadway support.The main research results obtained in this paper are as follows:(1)Based on the shear-slip model of the anchoring interface,the load transfer mechanism of the anchoring section of the anchor is studied,and the stress balance equation of the anchor solid-surrounding rock interface at the elastoplastic stage is established,and the analysis of the shear stress at any position of the anchoring interface and the axial force of the anchor is derived.solution.It is believed that the anchor solidsurrounding rock interface can be divided into the elastic deformation stage,the plastic softening stage and the residual shear stage.The shear stress distribution at different stages is different.At the same time,the influence of the calculation example on the anchoring performance of the bolt is combined.The factors have been systematically analyzed.(2)Developed the anchor rod confining pressure pull-out test system platform,and found a sealing material and method that can enable the test anchor solid sample to achieve a pressure of 0-40 MPa,which more reliably restores the resin anchor rod support process The real stress environment and state of the underground mine.(3)Through the cement mortar mix ratio test,three cement mortar mix ratio schemes meeting the compressive strength required by similar tests were determined,and three different strengths with uniaxial compressive strength of 15 MPa,30 MPa and 50 MPa were prepared.Cement mortar samples were used to simulate the surrounding rock of the roadway;through the bolt tensile test,the mechanical performance parameters of 18 mm,20 mm,and 22 mm bolts with different diameters were measured.The bolt body has undergone a total of elasticity during the tensile test.There are four stages: phase,yield phase,strengthening phase and contraction failure phase.(4)Based on the anchor rod confining pressure pull-out test system,through the resin anchor rod pull-out test,the effect of different confining pressures on the anchoring performance of the resin bolt is studied.The results show that as the confining pressure increases,the anchoring force of the anchor rod also increases,and the greater the confining pressure loading gradient,the more significant the impact on the anchoring performance of the anchoring system.In the low confining pressure range of 0?5 MPa,the change of confining pressure has a certain effect on the anchoring force of the bolt,but the overall effect is small;when the confining pressure exceeds 5 MPa,under the condition of medium and high confining pressure,the increase of confining pressure has a negative effect on the anchoring force.The improvement of the anchoring force of the anchor rod has a significant effect,and in the high confining pressure range of 15-40 MPa,the anchoring force of the anchor rod increases almost linearly with the change of the confining pressure.(5)Through the pull-out test of resin anchor rod under the same confining pressure,the influence of anchor rod diameter,anchoring length,and surrounding rock strength on the anchoring performance of the anchor rod is studied.The results show that when the three-diameter matching is satisfied,the larger the diameter of the anchor rod,the greater the anchoring force of the resin anchor rod;the longer the anchoring length,the greater the anchoring force of the resin anchor rod;the greater the strength of the surrounding rock,the greater the anchoring force of the resin anchor rod Bigger.