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Abstract There is a large-section box culvert jacking underpass expressway in Zhengzhou—Kaifeng city access project with the largest section size in China. Systematic monitoring work is arranged for the project，the deformation on expressway and the box posture control are focused on the whole jacking process. Monitoring results show that over half of total settlements appear after the first box section underpass on west side expressway；the southern region is over 60% and the northern region is over 54%；while the box culvert is jacked into the 3/4 width of the expressway，the deformation on expressway begins to speed up on both ends. Analysis shows that engineering characteristics such as thin coverage，large-section and unfavourable geological conditions are the main factors leading to large deformation on expressway；the fact that design idea has not been carried out in jacking process increases the deformation on expressway，which leads to poor quality in construction of pipe shed and pilot draft. By analysing the monitoring information of the box and the surrounding environment，some reference can be achieved in similar projects in the future.
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Received: 04 January 2009
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