Abstract:

There are many construction difficulties for Ziyang StationWuliting Station Shield Section on Fuzhou Metro Line No. 2, i.e. piles of Wuliting Overpass intruding into shield tunnel, low clearance, sewage pipe and small construction space. Hence, the secondary underpinning technologies for pile foundation, including bridge construction technology, temporary support by steel bailey beam, synchronous jacking, rope saw cutting and pile extraction by fullcircle slewing drilling machine, are put forward; and the socioeconomic benefits are analyzed. The study results show that: (1) By using the secondary underpinning technology for pile foundation, the maximum displacements of bridge crack, beam bottom, pounding bottom, underpinning system and point close to piers are 2 mm, 3.9 mm, 3.8 mm, 24 mm and 1.2 mm respectively; and the existing bridge and surrounding environment can be controlled. (2) Compared with traditional shield cutting piles after pile foundation underpinning method, the construction period and cost can be reduced by 2 to 3 months and 50% respectively by using the secondary underpinning technology for pile foundation; the adverse effects induced by surrounding complex environment can be overcome, and the risk of hyperbaric operation and cutting piles of shield can be avoided.

Key words: secondary underpinning technology, Fuzhou Metro, shield tunnel, pile foundation underpinning