Composite foundation pit supporting pile for soft and easy-to-surge stratum and construction method thereof

The invention discloses a weak easy-gushing stratum composite foundation pit supporting pile and a construction method thereof.The weak easy-gushing stratum composite foundation pit supporting pile comprises a composite supporting pile body formed around a foundation pit construction area, and the composite supporting pile body comprises an external waterproof curtain layer, a soil retaining supporting layer and a foundation water retaining reinforcing layer which are sequentially distributed at intervals from outside to inside; and joint filling foundation pit retaining layers are arranged between the external waterproof curtain layer and the soil retaining supporting layer as well as between the soil retaining supporting layer and the foundation water retaining reinforcing layer. According to the foundation pit supporting structure, gaps among the external stirring piles, the internal stirring piles and the cast-in-situ bored piles are filled with the high-pressure jet grouting piles, the high-pressure jet