共用围护相邻基坑

1、共用围护相邻基坑“先浅后深”施工技术潘伟强（上海隧道工程股份有限公司 ）摘要：地下空间开发中基坑群的施工面临着施工筹划和相互保护的技术难题尤其是共用围护墙，“先浅后深”施工风险更大。通过轨交、隧道工程和房地产开发相结合的地下综合体的施工数值模拟和实施数据分析总结出基坑群施工的关键技术和相互保护措施。关键词：轨交车站 相邻基坑 共用围护 先浅后深 施工技术地下空间的综合利用和开发是二十一世纪地下工程建设面临的难题。近年来，上海在 地下 空间规划方面采用了先进的 城市规划理念，并结 合城市自身的特点,开展了很多有益的尝试。目前，以轨 交建设为标志的地下空间 开发，不但 很大程 度上 缓解了城市交通

2、拥堵的难题，同时也 为地下商业 开发和地下多功能建筑一体化建设提供了前所未有的机遇t由于规划和技 术等方 面的原因，以往地 下空间 开发根据不同的功能和使用要求,往往形成先后开发多次建成。这些工 程位置相邻或 相近，经常面临 着地下空间 多次开发中的相互协调 、保护、相互连 通等难题。由于受某些条件的影响 ，相邻的基坑可能存在共用围护墙和“先浅后深”施工的要求这就 对后续施工的深基坑如何保护已有 的基坑结构提出了非常高的要求需要对其施 工技术和 保护措施进行进一步研究 。1工程概况上海轨交12号线国客中心站全长450 m宽15.830.6 m 采用地下墙围护 厚600 P00 mm深2629

3、m基坑开挖深 13.815.4 m设置45道钢支 撑。与车站基坑相邻的白玉兰广场有5个基坑其中3个基坑与车站共用地下墙，范围达到 270 m共用地 下墙厚1.0 m深51 m;其余地下墙深 42 m基坑开挖 深度22.124.1 m设置5道混凝土支撑（见图1）。tt tn阳畀m薛ii、mJ沁 th諾I W场日X图1 M1区和B区平面关系图工程建址内局部分布2砂质粉土，含有微承压水层顶埋深19.2 m水位埋深 2.7m，车站基坑需 要降压B区基坑将其隔断只需要疏干该土层。 层承压水埋深 43.9 m水位埋深7.3 m ,车站基坑不需要降压B区基坑有突涌风险 承压水降水深度约为4 m。土层的详细分

4、布见表1。表1 土层分布情况表土层土层名称层厚/m渗透系数/cm - s 11填土0 .802.801褐黄色灰黄色粉质黏土0 .70 2 .308.70 X10 -08灰色淤泥质粉质黏土1 . 40 7. 202.44 X10 -06j灰色黏质粉土0 . 40 901灰色淤泥质黏土7 . 50 -9 . 703.50 X10 一0711灰色黏土1 . 20-6.808.35 X10 一0712灰色粉质黏土3 . 80 8 . 501 . 15 X10 一062灰色黏质粉土2.90 12.201 . 68 X10 一0431灰色粉质黏土2.20 21.903.70 X10 一0633灰色黏质粉土

5、夹粉质黏土3.50 19.509.47 X10 -054灰绿色粉质黏土1 . 60 3 . 201草黄色黏质粉土1 . 00 5 . 501 . 59 X10 -042相邻基坑施工数值研究2.1 模型的建立本次计算采用平面应变数值模型完整建立M1区和B区基坑模型 基坑平面范围取80 m深度范 围取70 m模型中地下墙和土体采用4节点的平面 应变实 体单元 模拟，支撑采用2结点梁单元模拟 。模型总 单元数量为 5 519个总结点数为 6 747个，其中接 触面单元数为 200个。采用ABAQUS的分步计算和生死单元功能，整个基坑的施工过程共分18步，M1区基坑施工结束和B区基坑施工结束的模型图见

6、图2和图3。一 _ _ _-mviiiiiiHii i 丽丽丽丽 H 丽 iiiiiiiiiiiliiiiBliiiiiiiiijiijii iiiiiiiiiiiii iiimiiniiuiiiiiiiiiiiiiiiiiiiiiiiiiiiiii图2 M1区基坑施工结束模型图图3 B区基坑施工结束模型图2.2数值分析结果通过对建立的 数值模型进行模拟分析，可以得 岀施工过程中基坑结构 和土体的受 力变 形情 况，直 观揭示共用墙情况下相邻基坑“先浅后深”施工的受力变形特性和相互影响 。2.2 - 1地下墙水平位移在M1区基坑开挖过程中 M1区地下墙和共用 墙的侧向变 形发展与常规基坑相似

7、，呈中间大、两 端小的形状，随着开挖深度的增加 最大水平位移 位置不断下 移。M1区开挖结束，两侧地下墙最大 侧向变形位 于坑底附近,M1区地下墙最大变形为34.6 mm共用墙最大变形为48.4 mm。28 1QQ4-2014HOU SiM I M lit地煨俺瑞*门肿丁吩她辰EEMlT3DT4JT5DT6 地卜-給构顶扳变形监测点 1阳哋卜姑构底扳哽疗监测点DT7图6 围护墙顶和结构底板沉降点布置图4 - 2 围护结构数据分析下墙有下沉的趋势最大值达到24 mm,尤其是在 B1）地下墙沉隆数据分析（见图7） 区开挖第5、层土时 趋势更加 明显。监测到的7由图7可知：随着B区基坑开挖，共用地下

8、墙个断面沉隆情况基本一致整个结构向背离B区基有上抬的趋势最大值达到 20 mm M1区另一侧地坑一侧扭曲图7 M1区地下墙顶沉隆曲线图2）地下墙水平位移数据分析（见图8）由图8可知当B区基坑在车站底板深度以上开挖时 共用围护墙变形比较小约为15 mm基坑 再向深部开 挖时，下部地下墙变形明显，最 大达到28 mm。而上侧的地下墙则与车站底板为界，开 始向开挖的基坑内变形形成旋转式变形地下墙产生了反弯点。43内部结构数值分析1）结构内应力数据分析（见图9）。由图9可知在B区第6层土开挖至底板完成期间，车站中 板上排应力略有增加，下排应力略有 减小，在 B区底板完成后逐步恢复；在B区第6层土开挖至

9、底板完成期间，车站底板下部应力略有减小；在B区第5层开挖至第6层土之间 车站底板上 部应 力略有减小；在第6层土开挖至底板完成期间，应力趋于稳定直至B区底板完成后逐步恢复。2）结构沉隆数据分析（见图10）。由图10可知在B区基坑开挖期间，车站结构整体向B区基坑反向倾斜，在近共用墙位置顶板处最大上抬量达20 mm底板最大上抬达到15 mm。30 日期图9 底板应力变化曲线图白玉兰广场=|視逮土支撐IWMB 围绕已完成结构底板形成“S”形扭转。另外通过对上海轨交7号线静安寺站、号线世纪大道站等类似 工程实施过程数据的分析，上述扭转情形同样存在 爼是相邻基坑先浅后深施工普遍岀现的规律。aL Al 2

10、8 mm T f if5结语地下空间开发经常面临着相邻基坑施工的情况本工程的数值分析和工程实践为相邻基坑共用围护墙以及实施“先浅后深”的施工提供了经验 ，在 类似工程设计和施工中需要考虑二 次变形对内部结构的影响。IS4参考文献 张铭.地铁车站与地下综 合体一体化建 设肛世界科学， 2007 ( 10).图10 车站结构变形示意图通过数值分析和现场实测均表明共用地下墙的最终水平位移和沉隆基本一致浅基坑围护墙水平位移都向深基坑发展，与原变形叠加,共用围护墙及相 连内部结构向上隆起而另一侧向下沉降整体结构 王秀志特殊环境下地铁车站设计上海市轨道交通8号 线人民广场站结构设计 .地下工程与隧道200

11、5 ( 2).王庆 国既有轨道交通换乘车站改扩建工程基坑开挖变形预测及施工控制研究D1. 上海：同济大学交通运输工程学院，2008.(收稿日期：2013 -09 17)2013 年第4期地下工程与 隧道UNDEGROUNDENGNEERNGANDTJNNELSUNDERG ROUND ENGINEE RING AND TUNNELS(Quarterly) No.4 Dec. 2013Abstract of Main Contents(1) Settlement Rule and Prediction Method Study of Shield Tunn eli ng through Old

12、O ne-storey Houses WangFa, Lei Chonghong , Han Xuan , Zhou HongleiDepending on an interval tunne l of Beijing Rail Transit Line 8 , based on the Peck theory and stiffness modifying method for building settlemen t pred iction, the on-site deform ation m onitoring data is analyzed to study the settlem

13、en t rule of ground surface and old one -storey houses which is caused by shield tunne llin g in Beijing old city area , and construction settlemen t pred iction method is proposed .(5) Mechanical Behavior and Stability of Pipeline under Excavation Distur bance I mpact Ye Hui The article analyzes th

14、e deformation , stress status of underground pipelines and its coupling with the soil when the pipelines are subject to the influence of the excavation disturbance in soft ground . The study results have theoretical guidance for the risk analysis and mainten ance of urban utility pipelines .(10) Ex

15、peri mental Study on Load Bearing Capacity of Shield Tunn el Structure under Overload Cond iti on Liu Xian , Zhang Haoli , Lu Liang , Wang Xiuzhi Asa large quantity of loads on the ground will exert serious impact on the normal ope ration and secu rity of tunne l structure, a full-scale experimen t

16、is conducted to study the structural load bearing capacity of shield tunne l under overload condition . The test results show that: the load-displacemen t curve showing e lastic-plasticity , the load-displacemen t c urve rising almost linearly in the beginning stages of loading; when the concrete at

17、 joint compression zone is beyond the bolt position , stress mechanism of j oint changes causing the decrease of joint stiffness and even the structures whole stiffness; finally , the concrete at segmen t joint is compressed to damage and the overall structu re is deformed into a horizontal ellipse

18、with a relative displacemen t at the top and bottom of 153mm .(16) Comprehensive Development of Shanghai WuzhongRoad Rail Transit Depot Ma Z hongzheng, Zhu Beili ng, L i Yao , Jin Qi With the decreasing of urban land resources , comprehensive developmen t of rail transit depot is an effective way to

19、 achieve intensive use of land resou rces. Good developmen t project can effectively integrate and use urban land resources , guide the developmen t of urban structure and spatial morphology surrounding a block . And it is also an important measure to maintain s ustainable developmen t and virtuous

20、cycle of urban rail transit ope rat ion . In Shanghai Wuzhong Road Dep ot planning and c onstruction , the construction requ iremen t and phased imp lemen tation scheme are proposed based on the block position conditions analysis . The project has achieved initial success , the cumu lative experienc

21、e gained from which will be a good reference for similar projects .(21) Num erical Simulation Analysis of Unloading Effect of Extra- deep Excavati on C lose to ExistingRail Transit Station Yu L ongCombined with an actual case of Shanghai rail transit engineering , 2D and 3D numerical s imulations ar

22、e condu cted to study the excavation process of extra-deep excavation pit which is close to a rail transit station ( sharing a diaphgram w all) by ground displacemen t method, supe rpos ition principle and incremen tal method. Analysis is made to the internal force change and deformation trend of th

23、e existing station structure under the unloading e ffect of extra-deep excavation . And the rational control requ iremen ts are proposed for c onstruction of deep excavation pit.(27) Con struction T echnol ogy o f “ The Shallow Fir st and Then Deepfor Adjacent Excavation P its Sharing Retai ning Wal

24、l PanWeiqiang In underground space developmen t, construction of excavation pit group faces the techn ical difficulties of con st ructionplanning and mutual protection . Especially for the excavation pits sharing a retaining wall, it is more risky to construct the shallow excavation first and then d

25、eep excavation . Through construction numerical s imu lation and construction data analysis to the underground complex ( including rail trans it, tunne l and real estate developmen t ) , key technologies and mutual protection measures of c onstruction excavation pit group are summed up .(32) Con st

26、ruction A ppli cation of Soil M ixed Wall in Sandy Soil of Z hen gzh o u Guo Hao Soil mixed wall technique is seldom used in China Central Plain region. Combined the construction of retaining structure of work shaft ex cavation pit of Zhengzhou Zhongzhou Avenue Tunnel, it analyzes the construction d

27、ifficulties of soil m ixed wall technique , and introduces the equipmen t imp rovemen ts, construction parameter optim ization techn ology in detail. The success of constructing large diameter tri -axial mixed pile with H-shaped stee l in extra-deep sandy soil layer accumu lated experience for widel

28、y use of soil mixed wall in the futu re .(36) Resear ch and I nnovation of Joint Type of Diaphragm Wall Cao JiThe leakage problem is common in diaphragm wall const ruction, which is easy to result in the piping channel in excavation , posing a serious threat to the safety of project and its surround

29、ing environmen t. It is also a direct factor causing the leakage of internal structure and ground s ettlemen t later, wh ich has a major influence on the quality of the whole project.In order to prevent joint leakage of diaphragm wall, the most important is to adopt rational joint type which suits t

30、he engineering geological condition and working condition. Based on the advantage and disadvantage comparison of various joints , an innovative H-shape steel joint is proposed which is eithe r good at sealing e ffect or c ost-saving . It is recommended this new joint type shall be put into practice

31、as soon as possible through scientific research program and engineering tests.(42) Ventilation Environm ent and Fire in Rail T ransit Tunn el Zheng Jinli , Zhou Dan This article explains the relationship between ventilation environmen t and fire developmen t, analyzes the characteristics of tunne l

32、fire developmen t and propagation. Through numerical calculation and fire accident analysis, it pointed out that ventilation environmen t has a significant imp act on the fire developmen t, and proposed that changing factors of ventilation en vironmen t shall be important in fire acciden ts analysis

33、.(47) Application of Th ermal Count Statistical Technique in Interchange Passenger Flow Statisticof Shanghai Rail T ransit Chu ShengqiAs an imp ortant basis for passenger clearance and ope rat ion organization of rail transit in ter change station , inte rchange passenger flow statistic requires high accuracy and real-time . Thermal count statistical technique is a new solution for interchange passenger flow statistic, which will assist passenger clearance for automatic fare collection system and provide a reference for passenger guidance.(51) Di