Numerical Analysis of the Influence of Disc-Diameter Ratio of Helical Anchor in Clay on Uplift Bearing Capacity

螺旋锚是一种具有良好抗拔承载性能的基础型式，且具有施工便捷、适应性强和经济环保等优点，当前正在被大量应用于建筑、电力、交通、水利等多个领域的工程实践中。本文采用有限元方法建立盘径比D/d = 1~6的单盘螺旋锚拉拔数值计算模型，重点分析可塑黏性土中盘径比对螺旋锚上拔承载力及土体破坏模式的影响。结果表明：锚盘对上拔承载力起主要贡献。不同盘径比的螺旋锚，位移荷载曲线变化趋势基本一致，初始刚度与盘径比成反比，盘径比越小初始刚度越大。固定锚盘直径，随着锚杆直径增加，侧摩阻力增加，螺旋锚上拔承载力增加；但当锚杆直径增大到一定值时，由于锚盘净面积减小而明显影响锚盘承载力的发挥，螺旋锚上拔承载力反而下降。当D/d = 2时，螺旋锚发挥较好的抗拔性能。因此，建议在可塑黏性土应用螺旋锚时，为充分发挥锚盘上拔承载力，盘径比不应小于2。Spiral anchor is a kind of foundation type with good uplift bearing performance, and has the advantages of convenient construction, strong adaptability, economy and environmental protection. At present, it is widely used in construction, electric power, transportation, water conservancy and other fields. In this paper, the finite element method is used to establish the pull-out numerical calculation model of single disc screw anchor with diameter ratio of helix and shaft D/d = 1~6, and the influence of disc diameter ratio on the pull-out bearing capacity of screw anchor and soil failure mode in plastic cohesive soil is mainly analyzed. The results show that the anchor plate plays a major role in the uplift capacity. For spiral anchor with different diameter ratio of helix and shaft, the variation trend of displacement load curve is basically the same, and the initial stiffness is inversely proportional to the diameter ratio of helix and shaft. The smaller the diameter ratio of helix and shaft, the greater the initial stiffness. When the diameter of anchor plate is fixed, with the increase of anchor rod diameter, the side friction resistance increases, and the uplift bearing capacity of spiral anchor increases; However, when the bolt diameter increases to a certain value, the bearing capacity of the anchor plate is obviously affected by the decrease of the net area of the anchor plate, and the uplift bearing capacity of the spiral anchor decreases instead. When D/d = 2, the spiral anchor has better pull-out performance. Therefore, it is suggested that when the spiral anchor is applied to the plastic cohesive soil, in order to give full play to the uplift bearing capacity of the anchor disc, the diameter ratio of helix and shaft should not be less than 2.