PBA法暗挖施工是复杂地面环境下城市地铁车站施工的重要方法之一，开展PBA法暗挖地铁车站施工过程中围岩与支护结构变形、力学特性研究具有重要的工程意义。本文以西安地铁八号线某车站为背景，采用理论研究、数值模拟计算及现场监测相结合的手段开展研究工作，主要内容及结论为：

（1）对采用PBA法施工的西安某地铁车站关键施工节点作了分析，提出的合理的施工工序是：开挖上导洞→施作下导洞超前支护→开挖下导洞→铺设防水层，施作底纵梁→施作边桩与挖孔桩→施作中柱、冠梁与顶纵梁→开挖中间扣拱土体，施作初衬→错开中间扣拱一定步距后开挖两边扣拱土体，施作初衬→施作中间扣拱防水层及二衬→错开一定步距后施作两边扣拱防水层及二衬→开挖车站主体中板上部土体，施作中板及侧墙→开挖中板下部土体，铺设底板防水层，施作底板衬砌及侧墙→施作车站内部构件。

（2）建立地铁车站施工过程FLAC模型，完成了合理施工顺序数值模拟计算。模拟结果表明，导洞开挖阶段、桩柱梁体系施工阶段、扣拱施工阶段以及剩余土体开挖阶段所引起的地表沉降分别占总沉降的54.86%、15.60%、29.54%和0%。地表沉降在不同施工阶段变化明显。地表沉降曲线沿车站中线对称，主要影响区域在距车站20m范围内。随着车站的施工，地层沉降量增加，扣拱开挖完成后，随着地层埋深增加，地层变形增大。拱顶沉降与地表沉降的变化趋势大致相同。

（3）FLAC数值模拟结果表明，支护结构的应力峰值出现在中跨扣拱、顶纵梁底部、边桩和钢管柱顶部。边桩的压应力峰值出现在剩余土体开挖阶段，而其余结构的拉、压应力峰值则均发生在扣拱施工阶段。

（4）基于PBA法暗挖车站施工过程FLAC三维数值分析，对初支扣拱不同施工顺序的施工方案和二衬扣拱不同施工顺序的施工方案进行比选，通过对四种工况下初支扣拱和四种工况下二衬扣拱施工阶段的地表沉降、扣拱拱顶沉降、内力分析、对边桩中柱竖向位移的影响等4个指标的综合分析，验证了初支扣拱和二衬扣拱的最优施工顺序均为先中后边错距施工。

（5）完成了PBA法暗挖车站围岩及支护结构变形、受力监测方案设计并进行了现场监测，分析了PBA法车站施工过程围岩及支护结构变形及受力变化规律。现场监测结果表明：边桩迎土侧和中性面随着施工步序的进行，钢筋应力值增加，随着边桩深度的增加，钢筋应力值也增加。背土侧和迎土侧受力情况相反。扣拱应力峰值出现在扣拱拱顶位置，拱脚处有应力集中现象，与数值模拟结果一致；中柱各方向应力在中板以上土体开挖时最大，最大变形和压应力出现的位置为顶纵梁与钢管柱接触处；最大地层沉降值为22.48mm，在国家规范要求的控制范围内。

（6）对比分析数值模拟与现场监测结果可知，地铁车站PBA法施工诱发的地层变化趋势一致且施工诱发的地层变形值在国家规范允许的范围内。保证了地铁车站安全施工的同时，车站上方的市政三环主路正常通行。表明，监测方案设计可行，FLAC模拟计算参数合理，提出的施工顺序合理有效。

PBA method is one of the important methods for the construction of urban subway stations in complex ground environment. It is of great engineering significance to study the deformation and mechanical properties of surrounding rock and supporting structure during the construction of subway stations by PBA method. This paper takes a station of Xi 'an Metro Line 8 as the background, and uses the combination of theoretical research, numerical simulation and field monitoring to carry out research work. The main contents and conclusions are as follows :

(1) The key construction joints of a subway station in Xi 'an constructed by PBA method are analyzed. The reasonable construction process is as follows : excavating the upper pilot tunnel → constructing the lower pilot tunnel advance support → excavating the lower pilot tunnel → laying the waterproof layer, constructing the bottom longitudinal beam → constructing the side pile and the excavated pile → constructing the middle column, the crown beam and the top longitudinal beam → excavating the middle arch soil, constructing the initial lining → excavating the two sides arch soil after staggering the middle arch with a certain step distance, constructing the initial lining → constructing the middle arch waterproof layer and the second lining → staggering a certain step distance, constructing the two sides arch waterproof layer and the second lining → excavating the upper soil of the main middle plate of the station, constructing the middle plate and side wall → excavating the lower soil of the middle plate. Lay the floor waterproof layer, construct the floor lining and side wall → construct the internal components of the station.

(2) The FLAC model of subway station construction process is established, and the numerical simulation of reasonable construction sequence is completed. The results show that the surface settlement caused by the excavation stage of the pilot tunnel, the construction stage of the pile-column beam system, the construction stage of the buckle arch and excavation stage of the remaining soil account for 54.86%, 15.60%, 29.54% and 0% of the total settlement, respectively. The surface settlement changes obviously in different construction stages. The surface subsidence curve is symmetrical along the central line of the station, and the main influence area is within 20 m from the station. With the construction of the station, the ground settlement increases. After the arch excavation is completed, the ground deformation increases with the increase of the buried depth of the ground. The change trend of vault settlement and surface settlement is roughly the same.

(3) In FLAC numerical simulation, the peak stress of the supporting structure appears in the middle span arch, the bottom of the top longitudinal beam, the side pile and the top of the steel pipe column. The peak value of compressive stress of side pile appears in the excavation stage of residual soil, while the peak values of tensile and compressive stress of other structures occur in the construction stage of buckle arch.

(4) Based on the FLAC three-dimensional numerical analysis of the construction process of the underground excavation station by PBA method, the construction schemes of different construction sequences of the primary support buckle arch and the construction schemes of different construction sequences of the secondary lining buckle arch are compared and selected. Through the comprehensive analysis of the four indicators of surface settlement, arch crown settlement, internal force analysis and influence on the vertical displacement of the middle column of the side pile in the construction stage of the primary support buckle arch and the secondary lining buckle arch under four working conditions, it is verified that the optimal construction sequence of the primary support buckle arch and the secondary lining buckle arch is the first middle and then side stagger construction.

(5) The deformation and stress monitoring scheme of surrounding rock and supporting structure of PBA method underground excavation station is designed and monitored on site. The deformation and stress variation law of surrounding rock and supporting structure during the construction of PBA method station is analyzed. The field monitoring results show that the stress value of the steel bar increases with the construction step of the side pile and the neutral surface, and the stress value of the steel bar increases with the increase of the depth of the side pile. The back soil side and the soil side are opposite. The peak stress of the buckle arch appears at the top of the buckle arch, and there is stress concentration at the arch foot, which is consistent with the numerical simulation results. The stress in all directions of the middle column is the largest when the soil above the middle plate is excavated. The location of the maximum deformation and compressive stress is the contact between the top longitudinal beam and the steel pipe column. The maximum ground settlement value is 22.48 mm, which is within the control range required by the national standard.

(6) Through comparative analysis of numerical simulation and field monitoring results, it can be seen that the stratum change trend induced by PBA method in subway station is consistent and the stratum deformation value induced by construction is within the allowable range of national standards. While ensuring the safe construction of the subway station, the main road of the municipal third ring above the station passes normally. It shows that the monitoring scheme design is feasible, the FLAC simulation parameters are reasonable, and the proposed construction sequence is reasonable and effective.

[1] 《中国公路学报》编辑部. 中国交通工程学术研究综述2016[J]. 中国公路学报，2016，29(06):1-161.

[2] 钱七虎. 迎接我国城市地下空间开发高潮[J]. 岩土工程学报, 1998(01): 112-113.

[3] 肖茜. 北京地铁车站PBA工法施工对地表沉降影响的研究[D]. 中国地质大学（北京）, 2014.

[4] 杨军. PBA洞桩法工艺技术在地铁车站中的应用研究[J]. 城市建设理论研究(电子版),2019(35):34.

[5] 杨雄. PBA洞桩法在地铁车站施工中的应用[J]. 世界有色金属, 2017(01):46-47.

[6] 王军龙. 城市地铁施工中采用PBA法新思路[J]. 科技情报开发与经济, 2006(05): 292-294.

[7] 朱泽民. 地铁暗挖车站洞桩法(PBA)施工技术[J]. 隧道建设,2006(05):63-65.

[8] 李晓氽. 洞桩法(PBA)地铁车站施工关键技术[J]. 施工技术, 2017, 46(S1): 789-791.

[9] 李伟伟, 汪崎峰. 新型“PBA”法单层导洞洞桩一体化施工技术:中国铁道学会工程分会第七届线路专委会第二次会议[C], 中国天津,2017.

[10] 董贤顺, 孙秀荣, 闵向红, 等. “洞桩法”暗挖修建大跨浅埋地铁车站[J]. 建筑技术开发, 1996(02): 10-13+15.

[11] 张德华, 沈阿杏. 桩底后压浆技术在城市地铁车站洞桩法施工中的应用[J]. 现代隧道技术,2007(06): 70-73.

[12] 郭永军. 地铁暗挖车站扣拱施工技术[J]. 科技情报开发与经济, 2006(01): 294-295.

[13] Xuezhao Xu, ZhaoPing Li, Fang Qian, et al. Challenges and countermeasures for using pile-beam-arch approach to enlarge large-diameter shield tunnel to subway station[J]. Tunnelling and Underground, 2020, 98: 103326.

[14] B. Ralph Peck. Deep excavations and tunneling in soft ground[J]. Proc. 7th ICSMFE, 1969, 1969: 225-290.

[15] Attewell P B. Engineering contract, site investigation and surface movements in tunnelling works[J]. Soft-Ground Tunneling-Failures Displacements, 1981: 5-12.

[16] Xian Yang, Yongsuo Li. Research of surface settlement for a single arch long-span subway station using the Pipe-roof Pre-construction Method[J]. Tunnelling and Underground Space Technology, 2018, 72: 210-217.

[17] 侯学渊, 廖少明. 盾构隧道沉降预估[J]. 地下工程与隧道, 1993, (04): 24-32.

[18] 刘砥时, 方建勤. 弹塑性解析法确定隧道二衬合理支护时机的应用研究[J]. 公路, 2009(12):186-188.

[19] Bobet A. Analytical Solutions for Shallow Tunnels in Saturated Ground[J]. Journal of Engineering Mechanics, 2001, 127:12(1258).

[20] Wei-I Chou, Bobet A. Predictions of ground deformations in shallow tunnels in clay[J]. Tunnelling and Underground Space Technology, 2002,17(1): 3-19.

[21] Park K H. Elastic Solution for Tunneling-Induced Ground Movements in Clays[J]. International Journal of Geomechanics, 2004, 4(4): 310-318.

[22] J. Litwiniszyn. Fundamental principles of the mechanics of stochastic medium[C]. Proceedings of the 3rd Conference on Theoretical Applied Mechanics. India: [sn]. 1957: 18-26.

[23] R. J. Mair, R. N. Taylor, A. Bracegirdle. Subsurface settlement profiles above tunnels in clays[J]. Géotechnique, 1993, 43(2): 315-320.

[24] John H. Atkinson, David M. Potts. Subsidence above shallow tunnels in soft ground: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1977, 14(4).

[25] 高小州. 黄土地区地铁车站PBA工法施工沉降特性及稳定性研究[D]. 西安:西安理工大学,2021.

[26] 付春青. 地铁车站PBA法施工地层变形的时空演化机制及控制对策[D]. 徐州: 中国矿业大学, 2021.

[27] 陈庆章. 砂卵石地层中PBA工法导洞开挖顺序对地表沉降的影响[J]. 铁道建筑, 2017, 57(09): 81-84.

[28] Helmut F. Schweiger Ao, Pieter A. Vermeer Prof, Markus Wehnert. On the design of deepexcavations based on finite element analysis. Geomechanik Tunnelbau, 2: 333-344.

[29] 任伟明. 洞桩法施作地铁车站下穿桥梁影响研究[D]. 北京建筑大学,2014.

[30] 秦晓英. 城市地铁车站PBA工法施工力学效应的数值模拟研究[D]. 重庆大学, 2008.

[31] 张斌, 刘升传, 代维达, 等. 双层车站PBA法施工稳定性数值模拟分析[J]. 公路交通科技(应用技术版), 2015, 11(07): 232-233.

[32] 李储军. 适用黄土暗挖车站的改进PBA工法研究[J/OL]. 铁道标准设计: 1-10[2021-10-30].

[33] Qian Fang, Dingli Zhang, Louis Ngai Yuen Wong. Shallow Tunnelling Method (STM) for Subway Station Construction in Soft Ground[J]. Tunnelling and Underground Space Technology, 2012, 29: 10-30.

[34] 高成雷, 罗书学, 朱永全. 浅埋暗挖洞桩法的三维有限元模拟分析[J]. 石家庄铁道学院学报, 2002(03): 44-47.

[35] 刘波, 付春青, 聂亚抄, 等. 洞桩法施工对地表沉降影响的数值模拟及实测研究[J]. 施工技术, 2018, 47(04): 115-119.

[36] 李世久, 乔向进. 地铁车站洞桩法施工对地面沉降影响分析[J]. 兰州工业学院学报, 2020, 27(01): 38-43.

[37] 罗富荣, 汪玉华. 北京地区PBA法施工暗挖地铁车站地表变形分析[J]. 隧道建设, 2016, 36(01): 20-26.

[38] 张磊. 新型洞桩法暗挖地铁车站施工阶段地表变形研究[J]. 工程技术研究, 2020, 5(24): 32-33.

[39] 李金奎, 陈朋, 裴强. 复杂环境PBA法导洞施工顺序对地表沉降影响分析[J]. 广西大学学报(自然科学版), 2020, 45(06): 1276-1283.

[40] Jianchen Wang, YunGao Liu, Dingli Zhang, et al. Safety Control and Mechanical Response of Existing Tunnels Induced by Excavation of New Shallow Tunnel in Beijing[C]. DEStech Transactions on Materials Science and Engineering, 2017: 1-9.

[41] Xiangyu Guo, Zhengzheng Wang, Ping Geng, et al. Ground surface settlement response to subway station construction activities using pile–beam–arch method[J]. Tunnelling and Underground Space Technology, 2021, 108: 103729.

[42] Hao Wu, Baobing He, Guitao Luan, et al. Ground Settlement analysis of Metro Interval using PBA method in the Loess region[C]. IOP Conference Series: Earth and Environmental Science, 2021, 636(1): 012027.

[43] Qian Fang, Dingli Zhang, Louis Ngai Yuen Wong. Shallow Tunnelling Method (STM) for Subway Station Construction in Soft Ground[J]. Tunnelling and Underground Space Technology, 2012, 29: 10-30.

[44] 程灿宇. 地铁车站PBA法施工关键技术研究[D]. 北京建筑大学, 2013.

[45] Xinrong Liu, Yongquan Liu, Wanbo Qu, et. al. Internal Force Calculation and Supporting Parameters Sensitivity Analysis of Side Piles in the Subway Station Excavated By Pile-beam-arch Method[J]. Tunnelling and Underground Space Technology, 2016, 56: 186-201.

[46] Xinrong Liu, Yongquan Liu, Zhongping Yang, et. al. Numerical Analysis on the Mechanical Performance of Supporting Structures and Ground Settlement Characteristics in Construction Process of Subway Station Built By Pile-beam-arch Method[J]. Ksce Journal of Civil Engineering, 2016, 21(5): 1690-1705.

[47] Andrzej F. Tejchman. Model Investigations of Pile Groups in Sand[J]. Journal of the Soil Mechanics and Foundation Division, Proceedings of the American society of civil engineers, 1973, 2: 199-217.

[48] H. K. S. Ph Begeman, E. H De Leeuw. Horizontal earth pressures on piles as a result of nearby soil fills[J]. Proc. 5th ECSMFE. Madrid. 1972, 1: 3-9.

[49] Bransby M. F., Springman S. M. . 3-D finite element modeling of pile groups adjacent to surcharge loads[J]. Computer and Geotechnics. 1996, 19(4): 301-324.

[50] Tomio Ito, Tamotsu Matsui, Won Pyo Hong. Design method for the stabilizing piles against landslide-one row of piles[J]. Soils and Foundation. 1981, 21(1): 21-37.

[51] 张明聚, 晋刘杰, 刘义, 等. 地铁车站PBA工法施工变形风险管控实例分析[J]. 武汉大学学报(工学版), 2016, 49(06): 893-898+910.

[52] 董小龙. 青年大街站PBA工法大跨扣拱关键技术[J]. 山西建筑, 2009, 35(06): 156-158.

[53] 欧阳艳, 丁广炜. 管棚在PBA工法扣拱施工中的应用[J]. 漯河职业技术学院学报, 2011, 10(05): 56-57.

[54] 王岩, 林河恩, 文永刚, 等. PBA工法初支扣拱节点连接施工技术探讨[J]. 市政技术, 2016, 34(04): 76-80.

[55] 岳地东. 洞桩法暗挖多跨地铁车站二衬扣拱施工方法[J]. 工程技术研究, 2018(05): 75-77.

[56] 曾冰海. 洞桩法(PBA)暗挖多跨地铁车站扣拱施工[J]. 隧道建设,2010,30(04):456-460.

[57] 刘军, 吴玉勤, 荀桂富, 等. PBA工法中拱跨跨度对扣拱施工顺序影响的分析研究[J]. 市政技术, 2016, 34(01): 85-89.

[58] 刘明忠, 黄瑞金, 范京玲. 北京地铁10号线团结湖站洞桩法交叉部位扣拱施工技术[J]. 铁道标准设计, 2008, No.557(12): 209-211.

[59] S. P. Timoshenko, J. M. Gere, W. Prager. Theory of Elastic Stability, Second Edition[J]. Journal of Applied Mechanics, 1962, 29(1): 220-221

[60] 程鹏, 童根树. 圆弧拱平面内弯曲失稳一般理论[J]. 工程力学, 2005(01): 93-101.

[61] 陈先国. 隧道结构失稳及判据研究[D]. 西南交通大学, 2002.

[62] 李振华. 地铁暗挖PBA法车站钢管柱成孔施工技术研究[J]. 市政技术, 2022, 40(02): 80-85.

[63] 王文东. 地铁车站PBA工法钢管柱安装技术研究[J]. 铁道建筑技术, 2018, No.305(12): 15-18.

[64] 陈根龙, 宋刚, 崔淑英, 等. PA-10型钢管柱安装机的研制及在新型PBA工法施工中的应用[J]. 探矿工程(岩土钻掘工程), 2017, 44(07): 80-84.

[65] 王吉永. 大型地铁换乘站PBA工法应用探讨[J]. 西部探矿工程, 2008(12): 193-195.

[66] 裘湘波. 城市地下车站PBA工法扣拱施工技术[J]. 山西建筑, 2011, 37(07): 83-84.

[67] Qianen Xu, Wenmin Xu, Panshan Li, et al. A Hybrid Construction Method for Shallow Buried Urban Tunnel with Ultra-Small Clear Distance[J]. IOP Conference Series: Materials Science and Engineering, 2020, 960(3): 032007.

[68] Wu Bo, Huang Wei, YuFang Wu, et al. Optimization Principle and Application of Excavation Method for Large Section Metro Station[J]. International Journal of Engineering Research in Africa, 2021,52: 197-190.

[69] 黄瑞金. 地铁浅埋暗挖洞桩法车站扣拱施工技术[J]. 地下空间与工程学报, 2007(02): 268-271+276.

[70] 黄美群. 一次扣拱暗挖逆作法修建地铁车站新技术[J]. 都市快轨交通, 2009, 22(06): 66-71.

[71] 孟立民, 王珂, 冯澄宇, 等. 富水厚砂层地铁车站洞桩法施工降水关键技术及监测分析[J]. 现代城市轨道交通, 2022(11): 42-46.

[72] 张洪军, 冯利华, 周翠红, 等. 移动装配式模架在地铁站洞桩法施工中的应用[J]. 城市轨道交通研究,2022, 25(09): 157-159+165.

[73] 李家正, 杨浩杰, 冯吉利. 洞桩法导洞开挖方案分析与优化[J]. 科学技术与工程, 2023, 23(01): 307-313.

[74] Yongping Guan, Zhao Wen, Shengang Li, et al. Key techniques and risk management for the application ofthe pile-beam-arch (PBA) excavation method: a case study of the Zhongjie subway station[J]. The Scientific World Journal, 2014, 14: 275368.