地下开挖对既有桩基影响的模型试验研究

Model Test Study on Influence of Underground Excavation on Existing Pile Foundation

为分析地下开挖对既有桩基的影响规律,开展了大型室内模型试验,揭示了不同桩顶约束条件下桩基变形及内力的发展规律。分析表明:地下开挖对既有桩基的影响,很大程度上取决于桩顶的约束条件及既有桩基在开挖前的原位应力状态。相比较桩顶无结构约束的工况,工作状态下的桩基受开挖影响程度明显小于桩顶自由的情况。开挖前桩身原位应力越大,则桩顶回弹越小而沉陷愈加显著,并且上部结构顶板变形由隆起过渡为沉陷。

In order to gain insight into the influence of underground excavation on the existing piles,the large laboratory model tests were carried out.And the development rules of the deformation and internal force under different constrained conditions on the top of the piles are revealed.It is demonstrated that the influence of underground evaluation on piles mainly depends on two factors,i.e.,the constrained condition on the top of the pile and the in-situ stress state of the pile before excavation.Compared to the free-headed piles,existing piles are actually less affected by excavation.Higher initial force at the top of the pile before excavation leads to less rebound,more obvious settlement,and the upper structural roof deformation is caused by the transition from the uplift to the subsidence.