[关键词]
[摘要]
大直径嵌桩式重力锚利用嵌固桩的侧向承载作用增加抗滑力,可以减小重力锚体积,降低基坑开挖量和对原状地基的扰动、提高锚碇抵抗地质灾害的能力。然而,锚碇基底摩擦力和嵌固桩侧向承载力的联合抗滑机制尚不清楚,且缺乏可供设计使用的实用方法。针对中风化石英砂岩地基上的大直径嵌桩式重力锚碇,运用三维实体弹塑性数值分析手段,采用岩石力学中考虑高孔隙砂岩体积压缩屈服的帽盖模型和库伦接触-摩擦单元,分析了4根不同桩长大直径嵌固桩的侧向承载力以及单桩和群桩重力锚基底摩阻力和嵌固桩的耦合效应,揭示了重力锚嵌固桩侧向基岩反力分布形态和摩阻力随主缆拉力的演化规律,考察了嵌固桩长度以及平面布置形式对该类重力锚抗滑稳定性的影响。研究表明,重力锚嵌固桩可承担锚碇总抗滑力的70~80%,极限荷载下锚碇基底实际摩阻力只达到最大摩阻力的2/3。嵌桩式重力锚的抗滑稳定性系数可以达到悬索桥规范要求,而锚碇位移完全可以控制在跨度的1/10000之内。嵌桩式重力锚的失稳主要是由锚碇后部扩底式嵌固桩周围基岩局部屈服破坏引起。与传统重力锚相比,大直径嵌桩式重力锚可以减小锚碇自重达20%以上,对于大跨度悬索桥绿色建造具有重要的意义。 关键词:悬索桥;重力锚;嵌固桩;稳定性;抗滑
[Key word]
[Abstract]
The large-diameter pile-enhanced gravity-type anchorage has high anti-sliding capability through lateral load-resistance of the large-diameter piles, and thus has decreased volume and self-weight. As a result, the amount of excavation can be reduced and disturbance to the original ground can be reduced to a minimum. In addition, the piles can help resist the movement of the anchorage under geological disasters. However, the combined anti-sliding mechanisms of the rock-socketed piles with the friction between anchorage foundation and ground is unclear, and a practical design method is lacking. In this paper, the three-dimensional elasto-plastic finite element method is employed to study the lateral load-carrying capacity of pile-enhanced gravity-type anchorage. To do so, lateral resistance of rock-socketed piles with 4 different lengths are examined first, and then the coupled anti-sliding capacity of the pile with the foundation friction is investigated for the single-pile-enhanced and the pile-group enhanced anchorage on mediumly weathered sandstone. The cap plasticity model in geomechanics considering volumetric yield of high porosity rocks and the Coulomb contact-friction elements is used in the analysis. The reaction of the rock along the pile depth and the friction between the anchorage and the subsurface are analyzed. The influence of the pile length and layouts on load-carrying capability of the anchorage is examined. It is shown that the piles can takes up approximately 70~80% of the total anti-slide force, while the actual mobilized friction reaches only 2/3 of the limit value. The anti-slide stability factor of the anchorage is able to meet the requirement of the design code. With well-designed piles, the maximum horizontal displacement of the anchorage can be controlled within 1/10000 of the main span length. The failure of the pile-enhanced anchorage is caused by the yielding and collapse of the rock around the based-expanded piles on the rear of the anchorage. Compared to the stepped-bottom gravity anchorage, the pile-enhanced gravity anchorage can reduce the self-weight by more than 20%, and is beneficial for green construction of long-span suspension bridges. Key words:suspension bridge; gravity-type anchorage; rock-socketed pile; stability; anti-slide
[中图分类号]
x xxx.xx
[基金项目]
中国电建集团华东勘测设计研究院有限公司重大科技项目(KY2019-JT-22)