Study on Construction Optimization of Narrow and Long Foundation Pit Retaining Structure Compared with Elastic Fulcrum Method
[Purposes]The elastic fulcrum method is used to analyze the foundation pit as a plane strain problem,and that is,it is assumed that the long and narrow foundation pit is excavated once in a long dis-tance.However,there is a reality of segmented excavation in the actual construction,so it is necessary to study the influence of segmented excavation on the retaining structure of the foundation pit.[Methods]Combined with the narrow and long foundation pit in the open-cut section of the newly-built Aimin tun-nel exit of Ha-Mu passenger special line,a three-dimensional finite element model under different single excavation length conditions was established to study the variation of internal force and deforma-tion of the retaining structure with the single excavation length.[Findings]With the increase of single ex-cavation distance,the horizontal displacement and bending moment of retaining pile gradually increase and approach to the calculation results of elastic fulcrum method.When the excavation is 20 m,30 m and 40 m,the horizontal displacement increases by 8.75%,12.2%and 13.6%respectively,and com-pared with that when the excavation is 10 m,and the bending moment of pile body increases by 12.1%,14.9%and 16.8%respectively.When the excavation is 10 m,20 m,30 m and 40 m,the safety factors are 1.3,1.17,1.13 and 1.12 times of the elastic fulcrum method respectively.[Conclusions]The safety re-serve of the elastic fulcrum method is too large.In practical engineering,the enclosure structure can be reasonably optimized according to different excavation conditions,or the single excavation length can be reasonably adjusted when the conditions are met.
narrow and long foundation pitsectional excavationsafety coefficientelastic fulcrum methodthree-dimensional finite element
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