Study On The Action Mechanism And Application Of Wedge-shaped Expansion Type Internal Anchor Head

Prestressed anchoring technology has been widely used in water conservancy and hydropower,deep foundation pit and underground space projects due to its advantages such as fast construction,low project cost and remarkable reinforcement effect.In the case of prestressed anchor cable f ailure,the failure of anchor cable is often caused by the lack of pulling force.Aiming at the problem of insufficient pulling force in partial prestressed anchor cable,this paper presents a wedge-shaped internal anchor head with compression expansion ba sed on the mechanical characteristics of the internal anchor head of the prestressed anchor cable.This form of internal anchor head can change the stress state of the internal anchorage section from tension or shear to pressure or shear,give full play to the material characteristics of the compressive strength of mortar and rock material which is much higher than the tensile strength,greatly improve the anchorage force of the internal anchorage section of the prestressed anchor cable,and increase the overall reliability of the prestressed anchor cable.On the basis of the design of the Wedge-shaped expansion type internal anchor head,this paper studies the ultimate uplift bearing capacity and stress distribution around the anchor head by indoor tension test,and carries out the numerical simulation experiment combined with FLAC3 D and ABAQUS,and the numerical calculation results are basically consistent with the indoor tension test results The rationality of the numerical model and material parameters is explained.On this basis,the wedge angle of the Wedge-shaped expansion type internal anchor head is optimized by numerical simulation experiment.The results show that:(1)The stress state of the anchorage section of traditional prestressed anchor cable is mainly tension or tension shear.The Wedge-shaped expansion type internal anchor head transforms the stress state of the anchorage section into compression or compression shear through its wedge-shaped structural characteristics,which makes full use of the material characteristics of mortar and rock mass material,which is far higher than the tensile strength,and greatly improves the pull-out force of the anchorage section in the prestressed anchor cable.(2)The tensile test results of different types of internal anchor head show that the ultimate uplift capacity of conventional type internal anchor head is 174 k N,that of compression friction type internal anchor head is 153 k N,and that the internal anchorage section of Wedge-shaped expansion type internal anchor head steel strand with 10 ° wedge angle has not been pulled out after breaking(tensile load is 256 k N),and the pull-out characteristics of the Wedge-shaped internal anchor head is increased by more than 47%,which has obvious improvement The effect of anti pulling force.(3)Through FLAC3 D and ABAQUS,the numerical simulation tests of anchor heads with different wedge angles and different forms are carried out.The numerical simulation results are highly consistent with the test results.It i s further revealed that the wedge-shaped internal wedge anchor head can improve the stress conditions of the internal anchorage section and increase the ultimate uplift strength of the anchorage section.(4)Six different wedge angles were simulated numeri cally to obtain the curve of cyclic,axial and radial strain variation with wedge angles at the monitoring points.According to the curve characteristics,the wedge Angle of the wedge-shaped internal anchor head was optimized.The optimal design results showed that the optimal wedge Angle was 25° under the current design conditions.