Vacuum support excavation method suitable for deep foundation pit in complex stratum close to existing building

The invention discloses a vacuum support excavation method suitable for a deep foundation pit in a complex stratum close to an existing building. The vacuum support excavation method comprises the steps that stand column piles are arranged in a soil body of the wall of the foundation pit; a vertical drainage body, a vertical reinforcement body, a peripheral vertical closed curtain, a grouting bag, a transverse drainage body and a horizontal closed layer are arranged according to a designed range; vacuumizing is conducted through a vacuum pressure source, and foundation pit excavation is conducted; a slope sealing layer and vacuum nails are laid on the wall of a newly-excavated foundation pit, and an inner supporting system is arranged in the foundation pit; the slope surface sealing layer is sealed through a slope bottom vertical sealing curtain; and the permanent structure is constructed, follow-up dismantling, recycling and backfilling work is carried out, vacuumizing is stopped after the permanent structur