Immersed tube tunnel combination foundation and setting method

The invention relates to the field of immersed tube tunnels, in particular to an immersed tube tunnel combination foundation which comprises a PHC (prestressed high-strength concrete) rigid pile composite foundation, a natural foundation, a first sand compaction pile foundation and a mixed foundation. The PHC rigid pile composite foundation is arranged at the bottom of the upper section of an immersed tube tunnel island, the natural foundation is close to one end of the bottom of the middle section of an immersed tube tunnel, the mixed foundation comprises a second sand compaction pile foundation and a piling preloading structure, and the mixed foundation and the first sand compaction pile foundation are sequentially arranged between the PHC rigid pile composite foundation and the naturalfoundation. The invention aims to provide the immersed tube tunnel combination foundation and a setting method of the immersed tube tunnel combination foundation. By the aid of the immersed tube tunnel combination foundation,