Dense cast-in-place pile inner support foundation pit permanent support structure under complicated environment

The invention discloses a dense cast-in-place pile inner support foundation pit permanent support structure under a complicated environment. The structure comprises a first high-pressure jet groutingpile, cast-in-place piles, a second high-pressure jet grouting pile, a concrete hanging net, crown beams, inner supports, a gravel cushion layer, a reinforced concrete base plate and a foundation soilbody; the first high-pressure jet grouting pile is vertically arranged in the foundation soil body at the bottom of a foundation pit to form a composite foundation; the gravel cushion layer is pavedon the composite foundation; the reinforced concrete base plate is above the gravel cushion layer; the cast-in-place piles adopt reinforced concrete structures, and are vertically arranged in the foundation soil body; one sides of the cast-in-place piles on the outer side of the foundation pit are connected through the second high-pressure jet grouting pile, and the other sides of the cast-in-place piles on the inner side o