Cast-in-situ bored pile combined foundation pit support structure with reserved triangular soil and construction method

The invention discloses a cast-in-situ bored pile combined foundation pit support structure with reserved triangular soil and a construction method. The cast-in-situ bored pile combined foundation pit support structure comprises a cast-in-situ bored pile group located on the outer edge face of a foundation pit, a waterproof curtain is arranged on the outer side of the cast-in-situ bored pile group, and a reinforcing pile group is arranged on the inner side of the cast-in-situ bored pile group; a horizontal concrete supporting beam is further arranged at the top of the cast-in-situ bored pile group; the steel structure inclined strut is located between the horizontal concrete supporting beam and the foundation pit bracket; a triangular soil stacking layer is further arranged between the cast-in-situ bored pile set and the foundation pit bracket. The construction method comprises the steps that firstly, the pile foundation is constructed, then the horizontal concrete supporting beam is constructed, after the co