Vertical bearing behaviors of lattice shaped diaphragm walls and group piles as bridge foundations in soft soils

In order to investigate the vertical bearing behaviors and applicability of LSDWs as bridge foundations of high-speed railway in deep soft soils, three foundation modes (LSDWs with a single chamber and two chambers as well as group piles, respectively) with similar material quantity are studied through model tests. It is found that the settlements of LSDWs with a single chamber and two chambers are quite similar, while those of group piles are relatively large under the same loads. Compared to those of group piles, the ultimate bearing capacities of LSDWs with a single chamber and two chambers are increased by 16.7% and 20.4% respectively considering the settlement limits. The distribution of the skin friction for group piles appears to be an “L” shape, while that of the outer skin friction for LSDWS shows an “M” shape; and the inner skin friction of LSDWs is mainly aroused at the bottom of the wall. The most part of loading is shared by the tip resistance, which shows that the three modes are friction and end-bearing foundations. Both the loading sharing ratio of skin friction and soil resistance under caps of three modes are relatively small, which turns them out to be frictional end-bearing foundations. The unit tip resistance of group piles is larger than that of the LSDWs when subjected to the same loads, and the settlement of pile groups is also larger than that of LSDWs with the same unit tip resistance. For a practical bridge foundation, the bearing capacity and the settlement will be improved by using LSDWs instead of group piles in soft soils.