“洞桩法”暗挖车站施工阶段钢管混凝土柱承载力计算

北京地铁16号线部分车站为“洞桩法”暗挖车站，钢管混凝土中立柱底端嵌入桩基内。在当前设计规范及相关研究中，均未明确“洞桩法”暗挖车站施工阶段钢管混凝土柱承载力计算的柱底端约束条件。借鉴铁路桥梁、建筑桩基等高承台桩基竖向承载力计算方法，建立“洞桩法”暗挖车站施工阶段钢管混凝土柱承载力数值计算模型，对钢管混凝土柱初始偏心距对柱承载力的影响以及柱底端桩基对柱的约束作用进行分析。分析结果表明，在通常工程设计中，柱嵌入桩基长度满足规范要求及桩周为粉质黏土、卵石地层的约束条件下，可将“洞桩法”暗挖车站柱下桩基对柱底端约束条件简化为嵌固约束。

Bearing Capacity Calculation of Concrete filled Steel Tubular Column during Construction of Metro Station by PBA Method

Some metro stations on Beijing Metro Line No.16 are constructed by PBA method, and the bottom of the concrete filled steel tubular column is embedded in the pile foundation. In the current design codes and related researches, the constraint conditions of the bottom of concrete filled steel tubular column for the bearing capacity calculation during construction of metro station by PBA method are not cleared and identified. As a result, based on the calculation method of the vertical bearing capacity of the pile foundation of railway bridges and buildings, the numerical calculation model of the bearing capacity of concrete filled steel tubular column during construction of metro station by PBA method is established, and the influence of initial eccentricity on bearing capacity of concrete filled steel tubular column and the constraint provided by the pile foundation under the steel tubular column are analyzed. The analytical results show that under the constraints of column embedded in the pile foundation at a required length and the surrounding silty clay and pebble strata, the constraint conditions of the pile foundation under the column of PBA method station can be simplified into fixed constraints.