单螺旋锚桩水平承载机理试验与理论研究

目前螺旋锚桩水平拉拔承载设计计算的相关规范存在不足,理论研究中对锚片表面土压力分布的认识不统一。基于自制大型试验砂箱,开展了单螺旋锚桩的水平拉拔模型试验,直接量测分析了水平拉拔过程中锚片上下表面的土压力分布变化规律。引入考虑位移影响的锚片表面土压力近似计算方法,结合桩侧阻力p-y曲线,构建了砂土中单螺旋锚桩的水平拉拔力学模型,推导了位移相关的水平承载力计算理论。试验与计算结果表明：水平拉拔过程中,锚片表面土压力分布与测点到锚片中性轴的距离呈非线性关系,计算土压力时需考虑位移的影响;所构建的单螺旋锚桩水平承载力学模型以及基于力学平衡分析推导得出的单螺旋锚桩水平拉拔位移相关承载力计算理论在对比验证中取得了较好效果;对于工程中常用的单螺旋锚桩（桩锚直径比d/D≤5）,当埋深比大于4后,可不考虑锚片的作用,按照等直径的裸桩来计算其水平承载力。

Experimental and theoretical researches on horizontal bearing mechansim of single screw anchor pile

The design codes for screw anchor piles have shortcomings in calculation of the horizontal drawing capacity, and the understanding of soil pressure distribution on the anchorage surface is not unified in theoretical researches. A self-made large test sand box is used to carry out the horizontal drawing model tests on a single screw anchor pile. The soil pressures on the upper and lower surfaces of the anchor blade are directly measured to analyze the distribution rules. The displacement-related method is introduced to approximatively calculate the soil pressures, and based on the p-y curve of lateral resistance, a horizontal drawing mechanical model for the single screw anchor pile in sand is established, and the displacement-related theory is deduced to calculate the horizontal bearing capacity at last. The results show that in the horizontal drawing process, the soil pressure distribution on the surface of the anchor has non-linear relationship with the distance from the measuring point to the cental axis of the anchor, and the displacement should be considered in the calculation of soil pressures. The mechanical model and displacement-related capacity theory based on the mechanical equilibrium analysis have good effectiveness in the comparision validation. For the normally used single screw anchor pile (diameter ratio of bar to anchor d/D≤5), when the burried depth ratio is greater than 4, the horizontal capacity can be calculated according to the equal diameter naked pile directly, neglecting the effects of anchors.