Construction method of circular deep foundation pit enclosure of discrete pile support

The invention discloses a construction method of a circular deep foundation pit enclosure of a discrete pile support. The foundation pit enclosure is composed of bored piles in double row and in a delta form, inter-pile reinforcement and a waterstop curtain provided outside the bored piles, and a lining wall provided inside the bored holes. The foundation pit enclosure is characterized in that the bored piles in double rows and in the delta form make up a circular foundation pit, inter-pile earth is reinforced and waterproofed via high-pressure auger-injected piles, in-pit earth is also reinforced, the enclosure automatically closes under the stress action, the spatial effect of the circular structure is given to play, and the lining wall is reversely made along with excavation of a foundation pit. Compared with the prior art, the construction method has the advantages that the vertical enclosure is flexible to arrange and good in environment adaptability, the influence upon the surrounding environment is low, operating efficiency is high, the vertical enclosure is especially applicable to soft circular foundation pit projects with complex surrounding, many underground obstacles and high requirement on construction space, and engineering economic and social benefits are increased.