Static Mechanical Characteristics Analysis of Combined Helical Pile Composite Foundation Under Uplift and Horizontal Loading

The purpose of this study is to investigate the difference of static mechanical characteristics of combined helical pile （CHP） composite foundation under uplift-horizontal combined loading and unidirectional horizontal loading. The coupled Euler-Lagrange （CEL） method was used for finite element （FE） analysis. The accuracy and rationality of the FE model were verified by comparing the FE analysis results with the test results. This validated model was used to analyze the static mechanical characteristics， such as ultimate bearing capacities， initial stiffnesses， stress distributions and failure modes of the CHP composite foundation under the combined uplift-horizontal loading. When the uplift displacement was 0.2， 0.4， 0.6， 0.8， and 1.0 times the uplift control displacement， the horizontal ultimate bearing capacity decreased by 6.5 %， 11.3 %， 13.4 %， 17.3 %， and 22%， respectively， and the initial stiffness varied by no more than 4.5 %， showing that the method for controlling the ultimate bearing capacity using the limit lateral shift （e.g.， 40 mm） had a large enough safety margin. The plastic strain of the soil first appeared at the edge of the bottom anchor， then at the edge of the middle anchor plate， and finally gradually expanded upward through the upper and lower regions.