| Open surface method is widely used in 1st line of Chengdu metro station, which is under trunk road with high-rises buildings on both sides. There are many issues to be solved in the design and construction of excavation pit of subway station, though lot of experiment and achievement has been gained in deep pit excavation for high-rise building in Chengdu in recent decades.In this paper, the construction process of exaction pit of Jingjiang Hotel subway station was simulated with finite difference software FLAC3D. Combining with monitoring results, the mechanical behaviors of row pile retaining structure were obtained. The spatial effect and the influence on around environments caused by pit dewatering and excavation were studied. Following conclusions have been achieved:(1) The maximum horizontal displacement of retaining pile occurs at about 12m depth, which is two-thirds of the depth of excavation pit. The horizontal displacement at the bottom of piles is very small and can be ignored.(2) The maximum bending moment of pile is at about 14m depth. Negative moment never happens at the point of third steel brace, which is different from the calculating result of classical theory. The difference comes from that the deformation of pile before the installation of brace is not taken into account in classical method.(3) The bearing capacity of steel brace is far more than 1600kN, which implies that 1600kN is conservative as allowable axial force of the steel pile brace.(4) Prestressing on steel pile brace brings significant effect to reduce the horizontal displacement. But if only adding support in time, it can restrain effectively the distortion of supporting structure. (5) There is obvious spatial effect in the end of pit, the incidence is about two times the depth of excavation. The axial force of braces near corner of the pit is great than that of the braces at middle of the pit.(6) Distinct ground settlement around excavation pit due to dewatering is small. |
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