基坑开挖卸荷引起立柱桩的隆起位移计算

摘要

基坑开挖过程中坑底土体回弹隆起带动立柱桩产生向上的位移,对基坑支撑和围护结构的整体稳定性产生不利影响.在考虑基坑分步开挖、坑底土体回弹范围和支撑体系作用的基础上,基于剪切位移法建立了立柱桩位移的力学解析模型,并结合立柱桩的实际边界条件提出了基坑开挖过程中立柱桩位移的计算方法.通过现场实测数据对本文方法进行了验证,分析了土体回弹模量和分步开挖深度对立柱桩位移的影响规律,探讨了支撑产生的桩顶荷载对立柱桩隆起位移的影响.结果表明,本方法由于合理考虑了分步开挖和支撑体系的作用,因而计算结果与实测值吻合良好;坑底土体回弹对立柱桩隆起决定性作用,基坑开挖方式和土体回弹模量对立柱桩隆起位移影响较大,基坑支撑和围护结构对立柱桩的竖向位移起到很好的约束限制作用.%In the process of foundation pit excavation,the rebounding of the soil in the bottom of the pit has led to the upward displacement of the soldier pile,which have an adverse impact on the overall stability of supporting and retaining structure.Considering the stepwise excavation,the bottom soil resilience range and support system function,the mechanical analysis model of soldier pile displacement is established based on the shear displacement method,combined with the actual boundary conditions of soldier piles,a method for calculating the displacement of soldier piles in the process of excavation is proposed.The method is validated by field measured data,the influence of soil modulus of resilience and stepexcavation depth on the displacement of soldier pile is analyzed,the influence of pile toploadproduced by supporting strctureon the uplift displacement of soldier pile is discussed.The results show that this method is reasonable considering the effect due to stepexcavation and supporting system,and the calculated results are in good agreement with the measured values;The rebound of soilin the bottom of the pit is decisive to uplift of soldier pile,the excavation mode and the modulus of resilience of the soil have great influence on the uplift displacement of the soldier pile,the support and the retaining structure of the foundation pit play a very good constraint and restriction to the vertical displacement of the soldier pile.