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| Research on the Mechanical Characteristics of Asymmetrical Foundation Pit - in - pit Bracing System |
| JI Da – xue |
| (China Railway Siyuan Survey and Design Group Co. Ltd，Wuhan，Hubei 430063，China) |
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Abstract Abstract ： Research purposes ： Pit - in - pit is a kind of widely used asymmetric foundation pit，but the corresponding theory is not mature and cooperative research reports are few，so that the extent of the impact is always determined by experiences. Based on the underground engineering in Nanjing Youth Olympic Axis Project，with characteristics of upper cantilever and lower internal bracing，through the finite element analysis，the deformation of retaining structure of the is pit - in - pit asymmetry foundation and soil pressure distribution was studied，and the results can provide a reference for engineering design. Research conclusions ：( 1) The distance between inner and outer pit retaining，as well as the excavation depth of the inner pit affects the deformation and stress in pit retaining structure significantly. (2) As the distance between inner and outer pi retaining shrinks，the deformation of the inner pi，with a direction to the outer retaining，decreases continuously until bias to the inner pit，then the lateral earth pressure of the inner retaining structure can be calculated as the case of normal earth surface，while considering certain safety factor. ( 3 ) When the pit excavation depth increases，the lateral displacement to the outside of the inner pit also increases; when the inner pit has not been dug or the excavation is very shallow，the earth pressure on the pit retaining structure above the bottom is between the active earth pressure and the earth pressure at rest; when the pit excavation is deep $ the earth pressure above the bottom is close to active earth pressure，and to the bottom gradually approaching to the earth pressure at rest. (4) The research results provide valuable reference for analysis and calculation of similar projects.
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Received: 29 June 2016
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2016, Vol. 33 
