带帽刚性桩复合地基现场足尺试验研究

为深入、全面了解带帽刚性桩复合地基工作性状,通过在苏州绕城高速公路两试桩区的现场足尺试验,重点研究带帽刚性桩复合地基的荷载沉降、载荷板与桩体的沉降差、地表土应力分布特征、剖面沉降等性状规律。试验研究结果表明:带帽长桩型复合地基较带帽短桩型复合地基易于控制地基沉降变形和提高地基承载力,在设计荷载下带帽短桩型复合地基较带帽长桩型复合地基更能发挥地基土承载作用,桩帽下土体与桩帽间土体承载性能及发挥程度不同。由于桩帽能均化桩顶应力,起到刚性板作用,带帽桩体与桩帽下土体能产生近似等量的竖向变形,同时保证了垫层的整体效应。试验分析成果有助于建立带帽刚性桩复合地基计算模型、完善带帽刚性桩复合地基工作性状研究以及优化工程设计。

IN-SITU PROTOTYPE TEST STUDY OF COMPOSITE FOUNDATION OF RIGID PILE WITH CAP

In order to realize the working properties of the composite foundation of rigid pile with cap，the character laws were researched intensively by in-situ prototype test at the highway around Suzhou，such as Q-S，the settlement difference between load plank and pile，distribution of surface earth pressure，section settlement for composite foundation of rigid pile with cap. The results indicate that the composite foundation of long pile with cap is easier than the composite foundation of short pile with cap in controlling the settlement and enhancing the soil carrying capacity；the composite foundation of short pile with cap is easier than the composite foundation of long pile with cap in exerting the soil carrying capacity under the design load；the soil under pile caps is different from the soil beside pile caps in the load capability and its exerting extent；the vertical deformation is approximately same between the pile with cap and soil under pile cap；and the whole effect of the cushion can be ensured，because the pile cap can afford the rigid plank action and diffuse the stress on the top of pile. The test and analysis results are helpful to establish the calculation model of composite foundation of rigid pile with cap，consummate the theory of working properties of composite foundation of rigid pile with cap，and optimize the engineering design.