Study on vertical bearing characteristic of rigid pile composite foundation

To study the bearing characteristics of the composite foundation with rigid piles, a load test on a composite foundation with single pile was performed on the site of a certain building. In the test, a three-dimensional numerical model was built to carry out the numerical simulation of the load test. The simulation results were consistent with the actually measured data, indicating the validity of the simulation model. For the composite model with single pile, the effects of some factors, such as the pile length, the pile diameter, the pile spacing, the replacement rate and the cushion thickness on the bearing characteristics of the composite foundation were comprehensively analyzed. The result showed that the increase of the pile length was beneficial to improving the bearing capacity of pile, while an overlength pile would limit the pile side friction behavior. The increase of replacement rate could enhance the bearing capacity of the composite foundation and reduce the stress ratio of pile to soil, and further affect the bearing efficiency of pile. Based on the test results, a rational replacement rate was between 0.04 and 0.07. The cushion was helpful to coordinate the pile and soil to work together. When the cushion was set to be between 100 mm and 250 mm in thickness, it would bring little influence to the bearing capacity of composite foundation. According to the modeling results, a suggestion on the rational determination of various parameters is proposed.