西安洪庆地铁车站地基湿陷性研究

以西安地铁洪庆站为研究对象,针对现行“湿陷性黄土地区建筑规范”评价方法所得结果误差较大的问题,开展了现场原位试坑浸水试验,表明了该车站位于自重湿陷性黄土场地。通过数值分析方法,模拟车站施工过程,分析了不同埋深条件下车站基底分布实际竖向应力,揭示了地铁车站修建过程中地层内的卸荷特征,建立了不同埋深车站基底及围护结构基底竖向压缩应力分布函数。应用Flamant弹性解,建立了基底黄土实际竖向压缩应力随埋深变化的计算公式。通过结构压缩屈服应力与综合物理特征量的关系、压缩孔隙比与初始孔隙比比值与压缩应力与结构压缩屈服应力比值的关系,建立了计算浸水饱和黄土湿陷系数的“浸水结构破坏湿陷性”评价方法,并与现场试坑浸水试验结果进行比较,验证了评价方法的可靠性。对黄土地区城市轨道交通工程设计中湿陷变形量预测和地基处理深度的合理确定具有一定的参考借鉴意义。

Evaluation of Foundation Collapse of Xi'an Hongqing Metro Station

For the problem that there exist large calculation errors of the collapse deformation of foundation evaluated by the current "Code for Building in Collapsible Loess Areas", the in-situ test pit immersion test at Hongqing Station of Xi'an Metro, located in the self-gravity collapsible loess site, was carried out. Through the numerical analysis method, the actual vertical stress of the base distribution of different buried depth stations was analyzed by simulating the construction process of the station, and the unloading characteristics under the foundation of the station were revealed. The vertical compression stress distribution function under the foundation and enclosure structure of different buried depth stations is established. Based on the elastic solution, the calculation formula of the actual vertical compressive stress of loess strata varies with buried depth was established. Through the relationship between structural compression yield stress and comprehensive physical characteristic quantity, and the relationship between compressed pore ratio divided by initial pore ratio and compression stress and structural compression yield stress ratio, a method for evaluating the collapsibility of submerged saturated loess structure failure is established. Compared with the results of field test, the reliability of the evaluation method is verified. It has a certain reference significance for the prediction of collapsible deformation and the reasonable determination of foundation treatment depth in the design and implementation of urban rail transit engineering in loess region.