Study On Concrete Secant Pile Wall Being Applied In Deep And Large Subway Station Pit

Since 80's in 20 centuries, the exploitation and utilization of underground space has being attracted more and more attentions. The development of underground engineering causes pit deeply and largely, which becomes inevitable trend. The safe, economy and reasonable deep pit becomes a bit hot problem at present. Bored secant pile wall would be a new round of the retaining structures.Through the research of the paper, the writer hopes bored secant pile wall can be widely used in the soft land in the future. It offers practical experience for the new-type deep foundation pit supporting structure. Get the main conclusions as follows:(1) Teeming process of bored secant pile wall is emulated. Anti-permeability specimens are made in different time-intervals. Anti-permeability is studied by instrument. Optimum occlusion time-interval is 20~30 hours. The ability of occlusal surface decreases as the time- interval is longer. The whole ability of foundation pit supports declines, too. Utmost occlusal time is 60 hours, and construction Joints easily appears. Water seal is bad. The resultant is creatively.(2)By experiment resultants and theory analysis, the relation is gained between occlusion time- interval and the depth of supporting structure.(3) Bored pile is equivalent to 600mm diaphragm wall by rigidity method.Envelope diagram (displacement,moment, shear) is gained. Deep displacements reduce 13.8%. The moment reduces 15.5%. The shearing effect should be thought in the design.(4) The width of occlusion is the key factor for quality. Formula is d ? 2αL≥50mm.The pile verticality and occlusal width determine extreme pile length.