Research Of Embankment Lateral Deformation Effects On Piled Bridge Abutments On Soft Ground

Piles supporting bridge abutments on soft clay may be loaded laterally from horizontal soil movements generated by the approach embankment. Construction of embankments on soft clay results in the development of time dependant vertical and horizontal sub-soil displacements. Where the embankment on soft clay forms an approach to a piled bridge abutment, time-dependant movements within the clay may produce significant lateral loading and deflection of the piles. This loading, and any additional lateral loading derived from backfill earth pressure in cases where the approach embankment is retained by the abutment structure, will induce bending moments and deflections in the piles. In severe cases, this may lead to structural distress or failure of the piles or bridge structure.To solve the problems mentioned above, based on the systematic summary of existing theories, tests and analytical approaches, the behavior of piled bridge abutment against soil lateral movements has been studied thoroughly by FEM. The main contents and conclusions can be given as follows:Firstly, according to geotechnical literatures, the current research situation of embankment lateral effects on the piled bridge abutments on soft clay is analyzed. The field observation results and centrifuge model tests of piled bridge abutments on soft ground, finite element analysis of the soil-pile interaction and various computation techniques of the lateral earth pressure acting on the piles from horizontal soil movements are summarized.Secondly, displacement mode of unstable soil and the deformation mechanism of passive pile are analyzed, then a elastic perfectly plastic model and a hyperbolic curve model about the behavior of piled bridge abutment against soil lateral movements are developed on the basis of the previous research.In this paper, a plane strain finite element approach is described for analysis of pile groups influenced by lateral soil movements from the approach embankment in Lian Yungang. The piles are replaced by an equivalent sheet-pile wall with flexibility equal to the average stiffness of the piles and soil it replaced in the approach. Then, the relation between lateral deformation effects on the piled bridge abutment and the surrounding issues such as the thickness of soft clay, embankment height, loading speed is summarized. Some conclusions are drawn regarding application of the analytical method to the design problems of this nature.