高承载素混凝土桩复合地基现场试验研究

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。

Field tests on high-bearing composite foundation with plain concrete piles

The composite foundation with plain concrete piles is applied in the construction of a high-rise building.Various in-situ loading tests and stress tests of piles and soil are performed after excavation of foundation pits.The settlement and stress variations of the composite foundation are monitored during the construction period.Based on the test data,the work mechanism,load sharing characteristics of composite foundation,stress distribution of the piles,and settlement characteristics of the foundation are analyzed.Moreover,the effects of post-grouting technology of the piles on the work performances of the composite foundation are evaluated.The test results indicate that the composite foundation with plain concrete piles exhibits high bearing and small deformation capacities.The reinforcement without soil compaction technology has a reinforcing effect on the soil among piles.The application of post-grouting technology can improve the bearing capacity and reduce the settlement of the composite foundation,and high loading level may result in better reinforcing effects.The rigidities of the foundation slab and upper structure provide certain adjustment for non-uniform loads on piles.As a result,a variable rigidity design method based on the distribution of load and foundation pressure is proposed.