Numerical Analysis Of Bearing Characteristics Of Helical Anchors In Clay Soil

Helical anchor is a foundation with strong resistance to pullout and compression.The helical anchor foundation has the advantages of easy installation,less installation equipment,less noise and vibration during installation,movable and reusable,and higher bearing capacity after installation.At present,helical anchors are widely used in many fields,but the research on the damage mode and bearing mechanism of helical anchors under combined load and composite load is limited.Moreover,due to the distortion of the mesh around the anchor and the difficulty of convergence caused by shear expansion,the numerical simulation of finite elements around the helical anchor in clay soil has been little studied,especially for the deep buried anchor.In this paper,the numerical simulation analysis was carried out by ABAQUS,a large general-purpose finite element software,and the actual size of the three-anchor blade helical anchor in clay soil was established based on the numerical model validation by comparing with the transparent soil test and the one-way up-drawing test data of the helical anchor under oblique load.The load-displacement curves under each unidirectional load were obtained,and the effects of the first blade burial depth ratio and anchor spacing ratio on the bearing capacity of the helical anchor were analysed.At the same time,the effects of the burial depth ratio of the first layer blade and the anchor spacing ratio on the damage form of the helical anchor were analysed based on the equivalent plastic strain cloud and displacement vector cloud of the helical anchor under each unidirectional load.On the basis of obtaining the unidirectional load bearing characteristics,three load conditions,namely horizontal-uplift,horizontal-downforce and horizontal-moment-uplift,were applied to the helical anchor,and the effects of the burial depth ratio of the first layer blade and different ratios of horizontal loads on the uplift load bearing capacity of the helical anchor were analysed.The effects of the first blade embedment ratio and horizontal load on the damage form of the helical anchor were analysed.The study shows that:（1）the increase of the ultimate bearing capacity is affected by the increase of the first layer blade burial depth ratio L1/D is approximately linear,but when it reaches a certain depth,the growth effect is too obvious.According to the different forms of foundation damage can be S/D=2 as a helical anchor foundation anchor piece spacing ratio of the critical value,the design of the proposed anchor piece spacing ratio S/D>2.（2）horizontal bearing capacity by the first layer of the blade buried depth of influence is more significant.The influence depth of horizontal force is about 3D,if the main consideration in the project is horizontal action,L1/D≤3 should be selected.（3）When the downward compression load,when S/D≤2,the downward extrusion of the upper layer of anchor blades will affect the next layer of anchor blades,but when S/D>3,each anchor blade forms an extrusion zone almost independent of each other,and the load-bearing volume damage occurs.（4）Under the combination of horizontal-upward pulling loading,when L1/D is from 1 to 3,the upward pulling ultimate bearing capacity Uult increases significantly,when L1/D>3,it increases slightly,but the increase is not very obvious.（5）The influence of horizontal load on the downward pressure load is within 3%when the horizontal-downward pressure combination is loaded,so the influence of horizontal load on the downward pressure load capacity of the helical anchor is limited.（6）subject to horizontal-moment-upward pulling composite loading,the first layer of blade burial depth ratio L1/D from 1 to 3,upward pulling limit bearing capacity Uult significantly increased,when L1/D>3 slightly increased,but the growth is not very obvious.