为解决山区复杂环境下输电线路杆塔基础工程面临的挑战,本文提出了一种由短桩和桩周均匀布置的三根斜向锚杆组成的根桩基础,旨在提高桩基础的抗拉拔性能。通过开展现场真型试验,研究了根桩在上拔荷载作用下的桩顶竖向位移、斜锚轴力、破坏模式及荷载分配系数。结果表明:根桩基础上拔荷载-位移曲线可分为初始弹性直线段、弹塑性曲线过渡段和直线破坏段;在加载初期,斜锚杆承载作用表现不明显,随着荷载增加,斜锚杆轴力不断增大;根桩基础的极限抗拔承载力较短桩基础增加了29.41%,表明斜锚杆显著提升了根桩基础的承载力;根桩基础周围形成了径向和环向裂缝,主裂缝集中在斜锚杆布置区域,呈放射状分布,这是由于斜锚杆向上挤压岩土体,导致上方岩土体张拉破坏,最终使锚杆结构因受拉破坏而失效;对根桩基础的承载机制进行分析,短桩与斜锚杆的荷载分配系数可用于表征根桩基础的承载特性,二者协同受力;试验中,斜锚杆的荷载分配系数从加载初期的较低水平逐渐上升至48%,斜锚杆能有效分散和传递荷载。研究成果可为山区复杂环境下输电线路杆塔基础的设计和优化提供理论依据。
To address the challenges faced by transmission line tower foundation projects in complex mountainous environments, a root pile foundation composed of a short pile and three inclined anchor rods evenly distributed around the pile is proposed, aiming to enhance the uplift resistance of the pile foundation. Through field prototype testing, the vertical displacement of the pile top, anchor rod axial force, failure modes, and load distribution coefficient of the root pile foundation under uplift load were investigated. The results show that: The uplift load-displacement curve of the root pile foundation can be divided into three stages, including initial elastic straight line stage, elastoplastic curve transition stage, and the linear failure stage. In the early loading stage, the load-bearing capacity of the anchor rods is not significantly demonstrated, but as the load increases, the axial force of the anchor rods continues to grow. The ultimate uplift bearing capacity of the root pile foundation increased by 29.41% compared to that of the short pile foundation, indicating that the inclined anchor rods significantly improved the load-bearing capacity of the root pile foundation. Additionally, radial and circumferential cracks formed around the root pile foundation, with the main cracks concentrated in the area where the inclined anchor rods were arranged, presenting a radial distribution. This is because the anchor rods compress the soil and rock mass upwards, causing tensile failure in the upper soil and rock mass, and ultimately leading to the failure of the anchor rod structure due to tensile damage. Analyzing the bearing mechanism of the root pile foundation, the load distribution coefficient between short piles and inclined anchor rods can be used to characterize the bearing characteristics of the root pile foundation, and both components working together to bear the load. During the test, the load distribution coefficient of the inclined anchor rods gradually increased from a low level in the early loading stage to 48%, effectively dispersing and transferring the load. The research findings can provide a theoretical basis for the design and optimization of transmission line tower foundations in complex mountainous environments.
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