Abstract:

In light of the effective length problem of super-long pile of the pile group in highway bridges, the loading status of pile foundation for highway bridges in China is statistically analyzed. The resulting stress distribution range at the top of the pile is basically 6-21 MPa. The model tests of the super long pile groups have been carried out, in which the length-diameter ratio is 96 and the pile spans are respectively 3D, 4.5D and 6D. The axial force distributions of different loadings in the super-long pile group with different pile spans are obtained. According to the depth of pile section for axial forces of the pile tending to zero, the effective length of pile is determined. The relations between the pile top stress and the effective length of pile for three different pile spans are drawn up by utilizing the exponential functions. By exploring the resemble principles about model test of pile groups under the vertical loads, the effective length of piles corresponding to pile top loading of the super long pile group in highway bridges are yielded. Also the relations between the effective lengths of piles in the super long pile group and the pile spans are researched. At last, some suggestions are proposed for the concrete choice data of the pile spans and effective lengths of super-long piles.

Key words: highway bridge, stress of pile top, super-long pile group, effective length of pile, model test.