Discuss On Design Method And Construction Process Of The Ultra-deep Round Foundation Pit In Soft Soil Foundation

In engineering practice, people exploit and use underground space more and more; the development of most of the industrial and civil buildings foundation pit comes to deep and large. Excavation depth of city metro foundation pit is about 20m in general; and the super high-rise buildings such as Shanghai World Financial Center reach 25m; in municipal road and bridge, excavation depth of Wuhan Yangluo Yangtze River Bridge Anchorage is 46m; while the sheet iron recovery of hot rolling and continuous casting generally accepts rotational flow pool and its excavation depth is about 32m. When the excavation depth comes to some extent, the routine design and construction method could no longer meet the engineering need, especially in shanghai, which is the typical coastal soft soil area. The deeper of the pit excavation depth, the more risk to the engineering and construction. Whereas, this thesis use Pusteel Relocation Luojing Project 4200mm wide & heavy plate rotational pool project to simply discuss the engineering and construction method of this ultra-deep foundation pit.This foundation pit generally is designed to be round to full utilize the reasonability stress of round structure. While in soft soil, the corresponding pit building envelope should be made to round. However, there is no sophisticated design method in round supporting structure. Therefore, I collect calculation method and study development conditions about the Deep Foundation Pit Building Envelopes which have been built at home and abroad, and contrastively analysis the disadvantage about using current criterion calculation module to calculate round deep foundation pit building envelopes, and bring forward using improved conventional calculation method. Furthermore, I use the improved conventional calculation method to analyze Pusteel Relocation Luojing Project 4200mm wide & heavy plate rotational pool and contrastively analyze this result with original test result to verify the reasonability of the calculation method produced in this thesis.In construction, we accept comprehensive construction process, including "ultra-deep underground continuous wall" construction, "sectional half-reverse method structure construction excavation without support" technology, "deep pit decompression, precipitation and bottom dry closing" technology and "informationization monitoring" construction. The "ultra-deep underground continuous wall" construction successfully overcomes the limitation of mechanical design capacity through the method described in this thesis. The depth of channel reaches to 55m. And some negative phenomena easily happened in construction of underground continuous wall can be effectively controlled. On "sectional half-reverse method structure construction excavation without support" technology, the inside lining reverse construction process is determined according to structure style of ultra-deep foundation pit. It ensures the pit stability and safety of surroundings during excavation. On "deep pit decompression, precipitation and bottom dry closing" technology, on one hand the construction quality can be ensured. On the other hand, the dry working situation before closing bottom can be kept, at the same time, pit safety can be ensured under multi-layer confined water. On "informationization monitoring" construction, the monitoring result is the basis to direct construction on site, which would adjust construction procedure and time from time to time. It likes the eye of engineer during construction. Pusteel Relocation 4200mm Wide & Heavy Plate Rotational Pool Project obtained very excellent effect through this process. At present, this project has been put into production step by step.