预应力混凝土薄壁（PTC）管桩复合地基作为常见的基础型式在软土地区具有良好的实用价值和应用前景。在实际工程中，复合地基下卧层附加应力的确定一直是重点和难点，因此对PTC管桩复合地基应力扩散效应的研究具有十分重要的意义。针对天津软土地区进行了3组不同垫层厚度的复合地基现场静载试验，基于现场试验建立并验证了数值模拟方法，对比研究了该型式复合地基的承载特性；通过已建立的数值模拟方法研究了不同工况下PTC管桩复合地基的应力扩散现象，结合复合地基应力扩散理论确定了扩散角的取值范围，分析了土质、加固深度和外荷载对扩散角的影响规律。计算结果可为工程设计提供依据。

As a common foundation form, prestressed thin concrete (PTC) pipe pile composite foundation holds high practical value and excellent application prospect. In actual projects, the determination of the additional stress distribution of underlying stratum in composite foundation is the emphasis and difficulty. Hence, the study of the properties of stress dispersion of PTC pile composite foundation is of great significance. Three sets static load tests on composite foundations with different cushion thicknesses are designed and conducted in Tianjin soft soil area. Based on the static loading tests, the bearing characteristic of the PTC pile composite foundation are studied. The effect of cushion thickness on the bearing capacity is also studied. The numerical simulation method about PTC pile composite foundation is established and verified through the static loading tests. Through the numerical simulation method, the additional stress dispersion behavior of composite foundation in different geological conditions is studied and the scope of diffusion angles is determined. The influence of geological conditions, pile depth and the external load on the diffusion angles are indicated and the influence laws are carried out. The analysis results can be a good reference to the engineering practice.