Abstract: A pile-cap foundation system is an effective way to support an embankment in order to minimize total settlement. Due to the higher stiffness of the piles in relation to the surrounding soft soil, the vertical stresses from the embankment are concentrated on the piles. Soil arching develops as a result of differential settlements between the stiff pile caps and the soft ground between them. The three-dimensional arches span the soft soil and the applied load is transferred onto the piles and then the firm-bearing stratum. This research was initiated from the Shanghai F1 speedway project. Shanghai F1 speedway has been built on the typical soft ground of Shanghai. The fill of Shanghai speedway includes not only the lime fly-ash which has been widely used but also EPS which aimed to alleviate the total load; piled embankments method is employed at the region where the height of fill is relatively high. The field test has been done in Shanghai F1 speedway to investigate the distribution of earth pressure on the cap and between the caps. In addition, numerical method is used to in comparison with the field test results. The results show that the earth pressure obtained in the soil right above the cap is relatively higher than in the soil surrounding the cap. And the earth pressure distribution shows the same way for the soil lies on the edge of cap and the centre of cap. The influence of EPS and piles character on soil arching is discussed.

Key words: piled embankment, soil arching, FEM, EPS