Foam light soil structure applied to large-scale filling engineering and construction method

The invention discloses a foam light soil structure applied to large-scale filling engineering and a construction method. The foam light soil structure comprises a prefabricated three-dimensional specially-shaped foam light soil block and a cast-in-place foam light soil filling layer, the prefabricated three-dimensional specially-shaped foam light soil block is stacked in a groove or a mold cavityof roadbed engineering to form a gap or a channel for the foam light soil to circulate; the cast-in-place foam light soil filling layer is formed by filling gaps or channels of the prefabricated three-dimensional specially-shaped foam light soil blocks with foam light soil in a cast-in-place mode till the whole groove or mold cavity is filled with the foam light soil. On the one hand, hydration heat can be greatly reduced, the temperature stress is reduced, and cracking is effectively prevented; and on the other hand, the precast block body of the mold casting method plays a self-aggregate supporting effect on subseq