大吨位基桩抗压载荷试验中的锚桩预应力保护技术
REINFORCEMENT TECHNIQUES OF ANCHOR PILES FOR PILE BEARING CAPACITY TEST WITH LARGE VERTICAL LOADS
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摘要: 竖轴向承载力是桩基础设计的重要参数,现场静载试验是目前确定桩基承载力的主要手段之一。本文依托黄陵延安段高速公路洛河特大桥试桩工程,通过对原有工程桩施加预应力,形成了以工程桩为锚桩的锚拔体系。加载过程中试桩应力、锚桩应力及桩顶位移测试,结果表明,结合预应力技术,以工程桩作为锚桩构成桩基础静载试验的锚拔体系是可行的,同时提出了施加预应力大小的原则、方法以及确保后期曾作为锚桩的工程桩有足够承载能力应采取的必要措施。Abstract: Pile bearing capacity is an important parameter in foundation design.One of the key means to determine the pile bearing capacity is the conventional static load test at construction site.A pile testing project at Luohe Bridge along Huangling-Yanan Highway employs the piles of the bridge as the anchor piles.The anchor piles are stressed to form an anchor-pulling system.The test pile stress,the anchor pile stress and the displacement on top of the pile measured during the loading test show that it is feasible for the anchor-pulling system to use pre-stress technique and to take the piles of bridge as anchor piles for the static pile load test.At the same time,the equation is developed to determine the value of prestressing force applied to the anchor piles.Essential measures to make sure that those piles still have sufficient bearing capacity for the bridge after being used as anchor piles are also put forward.The results of this paper are of significance to shorten the construction period,reduce the test cost and broaden the application scope of prestressing techniques.
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