Analysis of cast-in-situ tubular piles in soft foundation improvement at bridge approaches

To study the performance and feasibility of tubular piles with geogrid reinforced macadam cushion, field test results, including settlement, lateral movement, pore water pressure, and pile-soil stress, are presented. The study indicates that the piles may improve the bearing capacity and meet engineering requirement on settlement with low cost, providing an economical and effective solution to the difficult problem of 'bump at bridge-head' with soft foundations. The geogrid can adjust the load distribution, thus causing the pile to carry more load and the foundation becoming more stable. Since the excess pore pressure is small, it has no influence on the stability of the foundation. Besides, the horizontal ground displacement is also small, thus the deformation rate decreases with time and depth.