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某高层建筑采用素混凝土桩复合地基。基坑开挖后,进行了多项原位载荷试验以及桩、土应力测试;在建造过程中,进行了沉降观测,并对复合地基应力变化做了跟踪测试。基于试验数据,对复合地基的工作机理、荷载分担特性、桩身应力分布特征、基础沉降特点等进行了分析,并探讨了桩底后注浆工艺对复合地基工作性状的影响。研究表明:素混凝土桩复合地基具有高承载力和低变形的性能;非挤土成桩工艺增强体,对桩间土也具有加固效果;采用桩底后注浆工艺,可提高复合地基承载力、减小变形,加固效果在高荷载水平下较好;基础底板及上部结构刚度对桩的不均匀受力具有一定的调整能力。提出了根据荷载和地基反力分布状况,采取针对性的变刚度调平措施的建议。
A high-rise building with plain concrete composite foundation. After the foundation pit excavation, a number of in situ load tests and pile and soil stress tests were carried out. During the construction process, settlement observation was conducted and the stress changes of the composite foundation were tracked. Based on the experimental data, the working mechanism, load sharing characteristics, stress distribution characteristics and foundation settlement characteristics of the composite foundation are analyzed, and the effect of the post-grouting process on the working behavior of the composite foundation is also discussed. The results show that the composite foundation of plain concrete piles has the characteristics of high bearing capacity and low deformation. The non-compacted pile forming technology reinforces the reinforcement of the inter-piles. The post-grouting process can improve the bearing capacity of the composite foundation , Reduce the deformation, the reinforcement effect is better under high load level; the rigidity of the foundation slab and the superstructure has some adjustment ability to the uneven bearing capacity of the pile. Based on the load and the distribution of the reaction force of the foundation, the paper puts forward the suggestion of taking measures to adjust the variable stiffness.