Mechanical Response Analysis on Construction of Diaphragm Wall in PBA Underground Excavation Subway Station
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摘要: 北京某地铁PBA暗挖车站采用边导洞内施工地下连续墙止水，在国内尚属首例。以该工程为依托，采用MIDAS软件模拟了PBA工法施工过程中洞内地下连续墙的力学响应规律，并与现场监测数据进行了对比分析。研究结果表明：（1）地下连续墙施工引起的地表沉降量较小，约占地表总沉降量的9%；（2）扣拱施工阶段、站厅和站台层开挖支护阶段地下连续墙水平位移变化较大，在实际工程中需对这三个施工阶段加强监测和施工控制；（3）地下连续墙竖向位移整体以隆起变形为主，沉降变形不明显，沿地连墙纵向各施工阶段中墙顶的沉降量略有波动，整体上趋近均匀分布；（4）车站主体结构施工完成后，地下连续墙墙体所受的拉、压应力均未超过混凝土抗拉、抗压强度允许值，地下连续墙结构处于安全状态。Abstract: Based on the first underground diaphragm wall water stop project constructed in the side pilot tunnel of PBA underground excavation station of urban subway in China, MIDAS software was used to analyze the mechanical performance of underground diaphragm wall in the construction process of PBA underground station, and the results were compared with the actual field monitoring data. The results show that: (1) during the whole construction process of the station, the surface settlement caused by diaphragm wall construction is small, accounting for about 9% of the total surface settlement. (2) The horizontal displacement of diaphragm wall changes greatly in the construction stage of buckle arch, the excavation and support stage of station hall and platform layer. In practical engineering, these three construction stages need to strengthen the control and monitoring. (3) In each construction stage of the station, the vertical displacement of diaphragm wall is mainly uplift deformation, and the settlement deformation is not obvious. Along the longitudinal distribution of diaphragm wall, the settlement of the top of the wall fluctuates slightly in each construction stage, and tends to be evenly distributed on the whole. (4) After the construction of the main structure of the station, the tensile and compressive stress of the diaphragm wall does not exceed the allowable value of the compressive and tensile strength of the concrete, which can effectively ensure the safety performance of the diaphragm wall itself.
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Key words:
- pile-beam-arch method /
- subway station /
- pilot tunnel /
- diaphragm wall /
- mechanical performance
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表 1 支护结构物理力学参数
结构
构件弹性模量
/MPa泊松比
ν重度
/（kN·m−3）黏聚力
c/kPa内摩擦角
φ/（°）初期支护 22000 0.25 23 地下连续墙 32500 0.25 25 二衬 30000 0.25 25 钢管桩 33500 0.25 25 注浆加固 90 0.3 21.5 30 60 
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表 2 岩土物理力学参数值表
土层
名称天然
重度
/(kN·m−3)黏聚力
c/kPa内摩
擦角
φ/（°）压缩
模量
Es/MPa泊松比
ν垂直
基床
系数Kv
/(MPa·m−1)水平
基床
系数Kx
/(MPa·m−1)杂填土 16.5 5 10 6 0.32 圆砾–卵石 20.5 0 34 40 0.3 50 50 卵石 22 0 38 70 0.3 70 60 卵石 22.5 0 40 95 0.3 80 80 卵石 22.5 0 42 105 0.3 80 80 黏土岩 22.5 50 30 30 0.28
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