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Abstract In order to clarify the law of ground surface deformation due to deep excavation in Beijing，a database of 30 case histories of field monitoring on Beijing subway stations is analyzed；and the results are compared with worldwide case histories. Research shows that：(1) The final pattern of ground surface deformation is“groove shape”；the maximum settlement is located at distances of about 10 to 15 m from the wall and occurs when the 1st to 2nd supports above the bottom are removed. (2) The maximum values of settlement，which range from 0.034%H to 0.316%H with a mean value of about 0.1%H，increases with the increase of H and decreases with the increase of insertion ratio. (3) The final values of deformation are less than the maximum ones. 75% of values of the monitoring points range from 0 to 20 mm，only 1.93% of that are larger than 30 mm. (4) Excavation can also lead to a small amount of ground upheaval；but the values of upheaval decrease with increasing excavation depth，and become very small finally. (5) Foundation pit deformation has obvious temporal and spatial effects；the settling rate increases gradually with time passing，excavation depth increasing，especially when drainage starts and the consolidation appears；but since the completion of the internal structure，deformation become stable. Values of deformation from transverse sections near the center of the excavations are largest and those from sections near the corners are the least. The settlement influence zone reaches to a distance of about 30 m from the excavation. The result can provide valuable references for the design and construction of similar projects in Beijing and other areas；it has great significance for preventing the foundation pit accident and avoiding the waste of resources.
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Received: 12 July 2011
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2012, Vol. 31 
