钻孔压浆混凝土预制管复合桩竖向承载力试验

目的研究一种新型桩基础——钻孔压浆混凝土预制管复合桩的成桩工艺、工作机理和单桩竖向承载力,为其在实际工程中应用提供合理的设计依据.方法通过桩的静载试验,并结合桩的工作机理,得到桩在黏性土和砂类土中的侧摩阻力和端阻力提高系数,建立单桩竖向极限承载力标准值计算公式.结果桩周土层为黏土、细砂、中砂时,桩极限侧摩阻力标准值提高系数分别为1.1~1.3、1.6~2.0、2.2~2.4.桩端持力层为细砂、中砂时,桩极限端阻力标准值提高系数分别为1.2~1.6、1.6~1.8.结论钻孔压浆混凝土预制管复合桩单桩竖向承载力较现行规范中经验公式算得的承载力数值有明显提高,研究成果对桩的设计和施工有一定指导作用,对这种新型桩基础的推广应用具有重要意义.

Experiment on Vertical Bearing Capacity of Composite Pile with High Pressure Bored Concrete Precast Pipe

A new type of pile foundation,namely composite pile with high pressure bored concrete precast pipe,w as studied in this paper. The piling technology,w orking mechanism and the vertical bearing capacity of this pile w ere researched. The improvement-coefficient of tip resistance and flank friction of pile in cohesive soil and in sand w as obtained by the pile dead load test. Combining the w orking mechanism,the calculating formulas for standard values of ultimate vertical bearing capacity of a single pile w ere built. It is found that w hen the soil around the pile is clay,fine sand or medium sand,the standard value improvement-coefficients of ultimate side friction of pile are 1. 1 ~ 1. 3,1. 6 ~ 2. 0,2. 2 ~ 2. 4,respectively; w hen the bearing course at the pile end is fine sand or medium sand,the improvement-coefficients are 1. 2 ~ 1. 6,1. 6 ~ 1. 8, correspondingly. Results show that the vertical bearing capacity of a single pile w ith high pressure bored concrete precast pipe is obviously higher than the value calculated w ith the empirical formula proposed by the current technical code. It is also indicated the results play a certain guidance for pile design and construction and have significance for popularization and application of the new type pile foundation.