适用黄土暗挖车站的改进PBA工法研究  

Research on Adaptability of PBA Improved Construction Method for Underground Station in Loess Area

作　　者：李储军[1,2] LI Chujun(China Railway First Survey and Design Institute Group Ltd.Xi'an 710043,China;Shaanxi Railway and Underground Traffic Engineering Key Laboratory,Xi'an 710043,China)

机构地区：[1]中铁第一勘察设计院集团有限公司,西安710043 [2]陕西省铁道及地下交通工程重点实验室,西安710043

出　　处：《铁道标准设计》2022年第6期97-104,共8页Railway Standard Design

基　　金：陕西省自然科学基础研究计划项目(2019JQ-938);国家自然科学基金项目(52078421)。

摘　　要：为研究PBA工法对于黄土暗挖车站适用性,解决传统PBA工法在黄土地层修建过程中存在的地基承载力不足及软黄土侧压力过大的两个难题。以西安地铁在建三拱双柱暗挖车站为背景,建立有限元模型分析PBA工法在黄土地层的改进效果,通过实测地表沉降数据对比及工程案例类比可知:上部四小导洞、下部两大导坑的改进PBA工法适用于黄土地层地铁暗挖车站修建;数值模拟中地表沉降与结构变形均符合规范要求,且与工程监测数据吻合较好;同北京地区同类型车站相比,地表沉降值不大;采用下部两大导坑先行开挖并施做底板以增强基底承载力,可减小地表沉降约19%,降低底部隆起约60%,显著提高洞室整体稳定性;向下开挖过程中,采用设置临时横撑可减小侧壁收敛约75%,有利于软黄土地层的边墙支护结构稳定。In order to study the applicability of PBA construction method in loess underground excavation station and solver the two problems as insufficient foundation bearing capacity and excessive lateral pressure of soft loess in the process of traditional PBA construction in loess stratum, a finite element model is established to analyze the improvement effect of PBA method in loess stratum based on the three-arch and double-column underground excavation station of Xi’an metro. The comparison of monitoring surface settlement data with engineering case analogy shows that the improved PBA method of four small pilot tunnels in the upper part and two large pilot pits in the lower part is suitable for the construction of underground excavation station in loess stratum. The numerical simulation indicates that the surface settlement and structural deformation meet the specification requirements, and are in good agreement with the engineering monitoring data. Compared with the same type of stations in Beijing, the surface settlement value is not big. The lower two pilot pits are excavated first and the bottom plate is constructed to enhance the bearing capacity of the foundation, which can reduce the surface settlement by about 19% and the bottom uplift by about 60%, and significantly improve the overall stability of the chamber. In the process of downward excavation, setting up temporary cross bracing can reduce the sidewall convergence by about 75%, which is conducive to the stability of sidewall support structure in soft loess stratum.

关 键 词：地铁 黄土地区 暗挖车站 改进PBA工法 适用性研究 

分 类 号：U231.4[交通运输工程—道路与铁道工程] U455.4[建筑科学—桥梁与隧道工程]