Construction method of roadbed shallow foundation reinforcing structure in plain area

A construction method of a subgrade shallow foundation reinforcing structure in a plain area comprises the following steps: forming a reinforcing main body of a shallow foundation by adopting a combined structure of capillary waterproof and drainage plates, a sand cushion layer, an anti-seepage geomembrane in a soil ditch, a lime soil cushion layer and impact rolling; if capillary water and underground water are separated by arranging the permeable geomembrane; due to the arrangement of the sand cushion layer, the drainage capacity of underground water is enhanced; an anti-seepage geomembrane is arranged in the earth ditch to prevent underground water from infiltrating after being drained into the earth ditch, so that the drainage efficiency is improved; the lime soil cushion layer is arranged to play a sealing role; an anti-seepage geomembrane is adopted in the ditch, and permanent and temporary combination is adopted, so that infiltration of underground water is avoided, improvement of soil body strength is