Deep Foundation Pit Excavation Procedure Optimization Considering Creep Deformation on Nearby Metro Tunnel
LIU Ji-qiang1,LI Yuan-hai2,LIN Zhi-bin2,GUI Chang-lin2
1.Beijing Jiaotong University, Beijing 100044, China; 2.State Key Laboratory for Geomechanics &Deep Underground Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
Abstract:Research purposes:The existing researches about excavating procedures of deep foundation pit on nearby metro tunnel in soft formation are lack of systematicness, and creep characteristics of soft clay are not usually taken into consideration. This paper takes Qianhaiwan station of Metro Line 11 in Shengzhen as engineering background and considers creep characteristics in sludge formation. The influence of step excavation in the transversal,longitudinal and vertical directions on the deformation of foundation pit and nearby subway tunnel are simulated, which may be expected to provide theoretical basis for choosing foundation pit excavation procedure of Qianhaiwan station.Research conclusions:(1) The segment far away from tunnel should be excavated firstly when only transversal step excavation was undertaken along the horizontal direction of foundation pit. (2)The maximum horizontal displacement of the piles show exponential relations with the number of segments when step excavation of foundation pit was undertaken in vertical and transversal or longitudinal. If thickness of every step excavation was limited in 1.5~2 m, the horizontal displacement of the pile near tunnel can be reduced about 9 percent when there is no horizontal step excavation. (3) Transversal step excavation with segments far from tunnel excavated firstly was found to be the best step excavation method under the same condition of step number and support, and longitudinal and transversal step excavation followed while longitudinal step excavation was the last. (4) The research results have guiding significance for foundation pit of Qianhaiwan station and similar projects.
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