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.