Abstract:Relying on the project of the rotating cable-stayed extra-large bridge spanning West Beitang Station for the Tianjin Freight Transportation Channel, aiming at the problem of high construction quality and safety risks of over 100 meters of bored cast-in-place piles in high-load group pile foundations under complex geological conditions such as soft soil foundation and liquefied soil layer in Binhai New Area, the consolidated expansion pile group technology is innovatively proposed. And the scheme optimization, construction technology and detection technique are studied. The results show that compared with the conventional bored cast-in-place pile, the optimized consolidated expansion pile can shorten the pile length from 100m to 72 m, effectively avoiding the quality risk of super-long pile collapse in soft soil areas. At the same time, the estimated cost of foundation pit support and foundation engineering has also been reduced from 78.28 million yuan to 37.59 million yuan, a cost reduction of 52%. Based on the reverse circulation pore forming technology, a device of integrated drill bit for drilling and reaming has been successfully developed, and a set of methods for determining the size of the disc cavity has been formed. The technical challenges such as efficient hole expansion construction in the disc cavity and the integrity testing of the disc cavity and concrete have been overcome. The research shows that the consolidated expansion pile technology has the significant economic, social and environmental benefits. At the same time, the significant increase in bearing capacity brought by consolidated expansion piles makes it possible to build bridges with longer spans and higher loads.
