洞桩法施工地铁车站地层变形特征研究

Study on Ground Deformation Characteristics of Subway Station Constructed by Pile-Beam-Arch(PBA)Method

采用洞桩法施工地铁车站对地层沉降具有良好的控制效果,因此,洞桩法被广泛应用于地铁车站施工。但洞桩法工序较多,引起的地层变形机理非常复杂,目前对洞桩法的系统研究还较为欠缺。针对于此,建立了洞桩法地铁车站的三维数值模型,系统分析了地层变形和地层塑性区变化规律,研究结果表明:导洞施工和扣拱施工是洞桩法的关键环节,地层变形主要发生在这2个阶段;地表水平位移关于车站轴线呈对称分布,导洞施工阶段和扣拱施工阶段引起的水平位移占总水平位移的82.7%;另外,地层沉降占总沉降的81.2%,且比重随埋深增大而逐渐增大;导洞施工引起地层产生塑性区,导洞施工结束时其周围的塑性区相互贯通,扣拱施工导致车站周围塑性区范围进一步变大,并逐渐向地表发展。该研究成果对洞桩法地铁车站施工具有一定指导价值。

The PBA(pile-beam-arch) method has been widely used in subway station engineering because it has good control effect on the ground settlement. However,the deformation mechanism of surrounding rock is complicated due to the construction procedure of the PBA method. It is lack of systematical research at present. A three-dimensional numerical model for the construction of subway station with PBA method is established in this paper and the changes of ground deformation and plastic zone of surrounding rock is systematically analyzed. The results show that : construction periods of Pilot tunnel and buckle arch which ground deformation mainly occurs in are the key links of the tunnel pile method. The horizontal displacement is symmetrical along the center line of the station,and the horizontal displacement caused by the 2 periods mentioned above accounts for 82.7% of the total ones. In addition,the ground settlement accounts for 81.2% of the total ones and its proportion gradually increases with the increase of the buried depth. The construction of the pilot tunnel causes the formation of a plastic zone in the stratum,and the plastic zone around the pilot tunnel is connected to each other after the pilot tunnel construction. The construction of the buckle arch leads to a further enlargement of the plastic zone around the station and gradually develops to the surface. The research results have certain guiding value for the construction of subway station by PBA method.