Research On Anchoring Effect Of Prestressed Anchor Cable In Loess Formation

Rock and soil anchoring system is an important part of large-scale geotechnical engineering.The anchoring effect of rock and soil determines the safety and long-term stability of rock and soil anchoring system.Rock and soil anchorage is developed rapidly and widely used due to its unique advantages.The anchorage section of the prestressed anchor is the main component of the anchoring system,which is the main force and force structure of the anchoring system.The stress state of the anchorage section has an important effect on the anchoring effect of the anchoring system.Therefore,the study of anchoring effect and load transfer is of great theoretical and engineering significance.In this paper,the load transfer and anchoring effect of prestressed anchor cable were studied deeply by field test,theoretical analysis and numerical simulation.The main research is as follows:1.Through the investigation,data collection and other means,the internal factors that affect the anchoring effect of anchor cable were taken as the research object,and a field test scheme for prestressed anchor was developed;The P-S curve of the anchor cable was obtained by field test of the prestressed anchor cable in the loess formation,and by changing the anchorage section length and the grouting ratio;The anchoring effect and failure mode of anchor cable under different factors were analyzed;The P-S curve model of the anchor cable pull-out test was summarized,meanwhile,the elastic displacement and elastic-plastic displacement of anchor cable under various loads of P-S curve were analyzed.2.Based on the shear slip constitutive model established by B.Benmokrane,the distribution law of the axial force in different deformation stages,anchoring layer interface shear force and deformation was deduced under the pull-out load,and the calculation formula of ultimate bearing capacity of anchorage section in elastic deformation stage and elastic-plastic deformation stage was given;Combined with theoretical analysis,the shear strength parameters1τ,1K in the elastic deformation stage of the anchorage section and the rock mass interface were obtained,and the shear strength parameters2τ,2K in the elastic-plastic deformation stage of the anchorage section and the rock mass interface were also determined.Combined with the P-S curve of the field test,the shear strength parameters of the field test were given,and the load transfer law of the anchor cable was analyzed with calculate examples.3.In the transverse direction,based on the Pasternak elastic foundation beam model,and the distribution law of the deflection,bending moment,shear force,corner angle and soil reaction force of the anchorage section was deduced under the transverse load.And the calculation method of the maximum shear displacement in the anchorage section was given under the transverse load and the failure zone of the anchorage section.Taking the loess stratum as an example,the force and deformation law of the anchorage section under the transverse load was analyzed,and the influence parameters were also analyzed.4.Combined with the shear stiffness parameters of the field test,the uτ-constitutive relation of shear slip was given.And combined with the shear slip constitutive equation for the nonlinear spring element in ANSYS to establish the F-D constitutive relation,the numerical simulation of the bond-slip relationship in the anchorage section was carried out.Based on the theoretical analysis and field test,it is shown that the numerical simulation of the bond-slip performance of the anchorage section was feasible,and it has some guiding significance to understand the load transfer law of the prestressed anchor cable and study on anchoring effect of the anchor.