南沙港区陆域软土基坑支护方案设计与实现

Design and implementation of soft soil foundation pitsupporting scheme in Nansha Port land area

为了有效消减建设于软土地基上的建筑物整体工后沉降,充分提高后续软土地基中基坑开挖的稳定性,依托广州港南沙港区办公楼软土基坑搅拌桩墙支护工程,进行了基坑支护方案的选型,分别对“先预压软基+后搅拌桩墙支护”与“不预压软基支护”2种备选工程方案进行了对比,同时采用直剪强度参数和φ=0法计算了地基的抗隆起承载力,并进行了对比分析。结果表明:对于研究项目,先预压可以显著提升土体的抗剪指标近一倍,实现搅拌桩墙深度和置换率的降低,从而降低工程造价;工程实测数据表明,计算中考虑φ会显著增加抗隆起安全系数,从而降低设计安全性;计算中考虑内摩擦角φ对土体抗力具有积极贡献,可以有效减少桩基布置密度。研究结果可以为工程中的土体设计参数选取提供重要依据,同时为类似基坑工程设计提供实用化参考案例。

In order to effectively reduce the overall post construction settlement of buildings on soft soil foundation and fully improve the stability of foundation pit excavation in the subsequent soft soil foundation,the foundation pit supporting scheme was selected based on the soft soil foundation pit mixing pile wall supporting project of Nansha port office building in Guangzhou port.The two alternative engineering schemes of"preloading soft foundation first and then mixing pile wall supporting"and"non preloading soft foundation supporting"were compared respectively.At the same time,the direct shear strength parameters andφ=0 method were used to calculate and analyze the uplift bearing capacity of the foundation.The results show that the preloading can significantly improve the shear strength of soil by almost 100%in this project,and reduce the depth and replacement rate of mixing pile wall,which results in the decrease of the project cost;the engineering measured data shows that the safety factors against the upheaval can be significantly increased by considering the internal friction angleφinto the calculation;the internal friction angleφhas a positive contribution to the soil resistance and can effectively reduce the pile foundation layout density.The research results can provide an important basis for the selection of soil parameters in engineering design,and provide practical reference cases for similar foundation pit engineering design.