PBA shallow buried underground excavating close range large section three-hole separated island type structure construction method

The present invention discloses a method for constructing a PBA shallow-buried subsurface excavation three-hole detached island type structure, which belongs to the design and construction range of an urban subway station. The method comprises the following steps: an underground pipeline of the upper part of a main body structure and a loose region or a hollow hole of stratum are detected; a transverse passage on the end part of the main body structure is constructed; a small pilot tunnel of an arch springing of a middle tunnel is constructed; a drilling and casting pile of the pilot tunnel, a crown beam of the top of the pile and a middle tunnel arch springing initial line structure model are constructed; a flat-type CRD construction method is adopted to carry out the construction of a side tunnel; a large step method is adopted to carry out the earthwork digging of the middle section of an arch part of the middle tunnel; the construction of the initial line structure of the middle tunnel arch part is carrie