Application of new Top-Down method in deep foundation

Abstract

Aiming at deficiency of cost higher in large area, and deep foundation pit excavation with conventional Top-Down method, A new Top-Down excavation method was introduced based on the general top-down excavation method. The key design techniques of the new Top-Down method include: using the temporary fender cast-in-place piles as exterior-protected construction in top-down excavation process; substituting level bracing system by basement slabs; combining the vertical structural supporting column with the temporary vertical shoring etc. A series of new techniques, including the profiled bar — concrete controlled bracing system, substituting level bracing system by variable level basement roof slap, several large diameter rings bracing on complex boundary condition, the top-down method of podium and the down-up method of turret etc. were first introduced and practiced in excavation engineering. It is shown that the new top-down method have good economic and social benefits. The method provides a new excavation engineering design choice for the similar pits, and the technology will be modified and improved in the future excavation design applications.