Time-dependent field performance of PHC pile-cap-beam-supported embankment over soft marine clay

Abstract

Routine capped rigid piles have been widely utilized to improve soft marine clay foundation for rapid construction of highway embankments and still exposed the problem of insufficient horizontal bearing capacity. An innovative composite system of pile-cap-beam (PCB) was presented in this study. Field measurements including pressures acting on the pile and soil surface, excess pore water pressures, settlements, lateral displacements and strains of ground beams were reported and discussed. The results elucidated that the response of ground beams subjected to embankment loading is closely related to the location of embankment corresponding to respective fill level. The beam between caps is prone to mid-span deflection at locations closer to the shoulder, which contributes to load transfer to the piles. The composite PCB system performed better in regard to reducing lateral displacements, total and differential settlements between the pile and surrounding soil, with a decrease of 57.1, 44.8 and 79.9%, respectively. The measured lateral displacement-settlement ratio suggested that the use of composite PCB system was remarkably effective in enhancing the stability of embankment. Moreover, feasibility of strain-based FBG sensors installed in the steel bar of ground beams was validated and limitations of the PCB system was also discussed in this study.