Construction method for complex geological section earth pressure balance shield passing middle air shaft

The invention discloses a construction method for a complex geological section earth pressure balance shield passing a middle air shaft. The construction method for a middle air shaft enclosure structure at the shield passing position comprises the following steps of: pouring a continuous middle air shaft enclosure wall, arranging four concrete supports on the enclosure wall, and reinforcing deep stirring piles of structural bottom plates; and constructing a plain concrete continuous wall on the outer side of the end enclosure structure to block a tunnel portal. A backfilling method comprises the following steps of: backfilling plastic concrete in a range of 3 meters, close to the tunnel portal, and backfilling cement stabilizing soil at the middle position. The construction method also comprises the following steps of: casting the structural concrete bottom plates, casting a side wall of a negative second layer to the position of 50 centimeters below the third support, performing horizontal hole prospection on the tunnel portal part, detaching the third support, and casting a structural concrete side wall to the position of 50 centimeters below a middle plate. Collapse accidents of the tunnel portal and serious safety accidents when an electrical park brake (EPB) shield reaches and a shield machine is buried can be effectively avoided under complex geological conditions; and secondary departure of the shield machine in the middle air shaft and related risks caused by the secondary departure can be avoided.