Centrifugal model tests on combined bearing characteristics of DCM and gravel foundation

The combination of DCM and gravel foundation is a new type of foundation form for dealing with complex geological conditions of cross sea immersed tube tunnels, which has extremely advantageous in soft soil areas. Based on the immersed tunnel project of Shenzhong-Zhongshan Bridge, centrifugal model tests are conducted to study the bearing characteristics of the DCM combined gravel foundation and the influences of excitation loads on the integrity of the DCM piles. The research results show that there is a turning point in the load-settlement curve of the composite foundation and a linear relationship between the load and the settlement before the turning point, and a steep drop after the turning point. The gravel foundation can effectively disperse stress and improve the overall bearing capacity of the foundation. The ultimate bearing capacity of the composite foundation is about 1.5 times the maximum load at the bottom of the immersed tube. When the upper load exceeds the ultimate bearing capacity of the foundation, the gravel will penetrate into the DCM piles, causing the pile head to break, with an impact range of about 3 m below the pile head. The surface settlement of the foundation is relatively small, and the post-construction settlement accounts for 15.5% of the total settlement. This new type of foundation form can effectively control settlement.