分离式车站洞桩法施工地层变形规律分析

Analysis of Stratum Deformation Rules in Separate Metro Stations Constructed by Pile-Beam-Arch Method

以北京地铁国贸站为工程背景，采用现场实测方法，研究分析了大跨度分离式地铁车站采用洞桩法施工，引起周围地层沉降变形以及拱顶沉降与地表变形的主要规律和影响因素。认为地层纵向沉降明显分为前期沉降、急剧沉降、沉降收敛区，而急剧沉降区分为导洞施工、扣拱、下部开挖3个阶段；横向沉降符合Peck曲线，影响范围为3-4倍洞径。拱顶沉降主要发生在扣拱以及下部土体开挖阶段，与地表变形相对应，如果扣拱施工、下部土体开挖、钢支撑支护比较及时，施工工艺合理，可有效防止土体持续松弛变形。

Taking the construction of Guomao station of Beijing Metro as example, the author studies and analyzes, by means of field measurement method, the main rules and effect factors that induce settlement and deformation of surrounding strata as well as crown settlement and ground surface deformation of large-span separate Metro station constructed by Pile-Beam-Arch method. The study result shows that the longitudinal stratum settlement can be divided into earlier settlement area, rapid settlement area and reducing settlement area. Rapid settlement area consists of heading construction stage, supporting arch stage and lower soil excavation stage; The traverse settlement accords with Peck curve and its influ- ence scope is 3 to 4 times of the tunnel diameter. The main crown settlement happens in the supporting arch stage and lower soil excavation stage, which corresponds to the ground surface deformation. If the supporting arch construction, lower soil excavation and steel supporting are carried out duly, the sustaining soil deformation can be prevented effective.Iv.