软土地区组合桩基础预制桩-水泥土-土体接触面摩擦特性及桩端承载性能研究

预制桩和水泥土组成的组合桩基础在我国东部地区已有了一些成功应用，但是目前对组合桩基础预制桩-水泥土-土体接触面摩擦特性和桩端承载性能的研究较少，缺少对组合桩基础荷载传递机理的系统性研究，没有合理的组合桩基础承载力和沉降计算公式。本项目通过桩土接触面剪切试验、模型试验、现场试验、解析计算和数值模拟等方法对软土地基中组合桩基础预制桩-水泥土-土体接触面的摩擦特性和破坏模式进行系统研究，揭示预制桩桩身形状、桩身表面粗糙度、水泥土强度、水泥土尺寸、围压水平对预制桩-水泥土-土体接触面摩擦特性和破坏模式的影响规律；探明桩端位置处预制桩-水泥土接触面摩擦特性和破坏模式对组合桩基础桩端承载性能的影响规律；建立预制桩-水泥土-土体接触面摩擦模型和桩端荷载传递模型；考虑桩周和桩端水泥土变形特性影响，提出软土地基中竖向受荷组合桩基础承载力和沉降计算公式，为实际工程中组合桩基础的设计和推广提供理论依据。

The precast pile-cemented soil composite (PCSC) pile has been successfully used in some practical projects in Eastern China. While little research has been conducted to investigate the frictional capacity of precast pile-cemented soil-soil interface and base bearing capacity of PCSC pile. The load transfer mechanism of PCSC pile is not well studied, and there is no rational formula for the calculation of bearing capacity and settlement of PCSC pile, which hampers the promotion and application of PCSC pile. In this project, pile-soil interface shear tests, model tests, field tests, numerical simulation and analytical calculation will be used to investigate the frictional capacity and failure mode of precast pile-cemented soil-soil interface of PCSC pile embedded in soft soil foundation. The influence of precast pile shape, shaft surface roughness, cemented soil strength, the scale of cemented soil zone and confining stress level on the frictional capacity and failure mode of precast pile-cemented soil-soil interface will be studied and clarified. The influence of frictional capacity and failure mode of precast pile-cemented soil interface at pile base will also be investigated. Finally, the precast pile-cemented soil-soil interface friction model and the pile base load transfer model will be built, and the formula for the calculation of bearing capacity and settlement of PCSC pile under compression in soft soil foundation will be proposed by considering the deformation characteristics of cemented soil along shaft and at pile base. The research results will provide a basis for the design and promotion of PCSC pile in practical projects.