Experimental and Theoretical Research on Uplift Bearing Characteristics of Helical Anchors in Self-Weight Collapsible Loess

To investigate the uplift bearing performance of helical anchors in self-weight collapsible loess， in-situ experiments and CEL numerical simulations were conducted on helical anchors embedded in collapsible loess， based on an ultra-high voltage project. This study revealed the force-displacement relationship of helical anchors under uplift load in collapsible loess， clarified the stress and strain distribution patterns of the soil surrounding the helical plates， and elucidated how these patterns varied with the spacing between helical plates. Furthermore， the failure modes of helical anchors in collapsible loess were identified， and a bearing capacity calculation formula tailored to different displacement control conditions was established. The results indicated that when the limit state of helical anchors was governed by displacement， the contribution of soil internal friction angle to bearing capacity could be neglected. During uplift， the maximum strain initially occurred in the bottom helical plate， followed by the intermediate helical plate， and gradually extended upward to encompass the entire region. When the spacing between helical plates was 1D（D=anchor plate diameter）， the helical anchor experienced overall shear failure of the soil between plates. Conversely， at a spacing of 3D， independent failure of individual helical plates occurred. At a spacing of 2D， the failure mode of the helical anchor lay between these two extremes. The bearing capacity calculated using the overall shear method for soil between helical plates agreed well with the experimental bearing capacity determined by the 10%D method. Additionally， the minimum calculated bearing capacity， which incorporates both the overall shear failure of soil between helical plates and local failure of soil around helical plates， agreed well with the experimental bearing capacity determined by a 50 mm displacement criterion.