Research conclusions: As a new type of foundation protection structure，it makes the full use of the geological conditions to take the reinforced concrete pile as the vertical support beam，and uses the level bound of the foundation rock on the pile bottom end and the level bound on the periphery beam of the fore shaft on the pile top end to form a stable self －locking support system to avoid making the support system in every steps during the foundation excavation． The plain concrete pile and reinforced concrete pile are nested to form a water － stop curtain to fully stop the water that is not achieved by the boring piles． In this way，the boring cast pile is used as the support structure and at the same time as the water － stop curtain to overcome the problems of the poor waterproof property and low safety，and at the same time it effectively cuts the construction cost．