Study of Design and Construction Technology of Ultra large span Tunnel at Badaling Great Wall Station（八达岭长城站超大跨度隧道设计施工技术研究）

The large span transition section at Badaling Great Wall Station with a maximum excavation span of 32.7 m and an excavation area of 494.4 m2 is the traffic tunnel with the largest excavation span and excavation section area in the world, resulting in substantial construction difficulty and high safety risk. To ensure the construction safety of Badaling Great Wall Station, the support parameter design, a new excavation method, and the surrounding rock deformation control principle for tunnels with an ultra large section are studied. The study results show that: (1) According to the checking calculation, the support system had a safety factor of 1.16-2.46 during the construction period and 1.59-3.54 during the operation period, i.e., its engineering structure is safe and reliable. (2) The innovative triangle type excavation applied to the tunnel with an ultra large span and section has the advantages of a simple and clear method, safe and reliable structure, high applicability of mechanical equipment and high construction efficiency. (3) Depending on different surrounding rock classes and spans, the criteria for total deformation control of the large span transition section at Badaling Great Wall Station are as follows: in the case of class Ⅱ surrounding rock, the total settlement is 20-30 mm, and the total horizontal convergence is 15-20 mm; in the case of class Ⅲ surrounding rock, the total settlement is 30-40 mm, and the total horizontal convergence is 20-25 mm; in the case of class Ⅳ surrounding rock, the total settlement is 60-90 mm, and the total horizontal convergence is 40-55 mm; in the case of class Ⅴ surrounding rock, the total settlement is 130-190 mm, and the total horizontal convergence is 90-105 mm. (4) According to the numerical simulation, the innovative triangle type excavation method results in deformation that is mainly centralized in the tunnel arch making stage, accounting for approximately 95% of the total, followed by deformation in the side making stage, accounting for 4% of the total, with the smallest deformation only accounting for 1% in the inverted arch making stage.     

Design Method and Application of Rock and Support System for Super large Span Tunnel（超大跨度隧道围岩支护体系构件化设计方法及其应用研究）

In order to guarantee the stability of surrounding rock and support structure of super large span tunnel and realize quantification of support structure design, the optimal excavation contour line shape is obtained based on study of influence of initial ground stress on bearing arch of surrounding rock; a new quantitative design method, in which the surrounding rock is regarded as an arch structure, bolts, cables, shotcrete and lining are designed to satisfy the intensity, rigidity and stability of the arch structure, is presented to design the support structure system. The method has been successfully applied to super large span tunnel of Badaling Great Wall Station on Beijing Zhangjiajie High speed Railway; and the applicable results show that the maximum accumulative settlement of crown top of large span section is only 17.3 mm, and the relative subsidence of crown top is only 0.09%, which can meet safety requirements.     

Prospect of Infrastructure Construction under "Belt and Road" Initiative（“一带一路”的基础设施建设前景）

The process of how the "Belt and Road" Initiative was brought up is studied and the major opportunities that the "Belt and Road" Intiative brings to China are described in this paper. The "Belt and Road" Intiative is very prospective. The important role of the infrastructure construction in the "Belt and Road" Intiative is shown. Two examples of the infrastructure construction under the "Belt and Road" strategy, i.e., China Nepal India Trans Himalaya Corridor and Kra Isthmus Canal in Thailand, are introduced. Finally, the challenges that China will face in the infrastructure construction under the "Belt and Road" Intiative and the rational countermeasures are described.     

锦屏二级水电站深埋特大引水隧洞关键技术

Seven tunnels across Jinping Mountain are arranged for Jinping Ⅱ Hydropower Station, with a total length of about 120 km. Among them, four headrace tunnels have a length of 16.67 km, an excavated diameter of 12.4-14.6 m, and a cover depth of 1 500-2 000 m in general. The maximum cover depth is 2 525 m, and the maximum external water pressure is more than 10 MPa. The tunnels are featured by great length, great depth and large diameter. It is the largest and most difficult among the underground tunnel groups built or under construction in China and even the world. With complex hydrogeological conditions and special topographical conditions along the tunnels, many challenging problems, such as rock burst under high in situ stresses, groundwater inrush in karst strata and failure of loading bearing structure, were encountered during construction. A great amount of groundbreaking studies were carried out regarding these problems. The key technical problems during construction of extremely large and deep tunnels were solved successfully. Safe and rapid tunnel construction and stable operation were achieved. The hydropower station started operation in 2014 and has been in a safe and stable operation state. The successful construction of headrace tunnels of Jinping Ⅱ Hydropower Station can provide some experiences and reference for deep tunnel projects in the world.     

Construction Behavior of Double Down?side Drifts in a Weak Tunnel with Shallow Cover

Confronted　with　accidents　in　a　shallow?buried　weak　tunnel　using　the　bench　excavation　method,such　as　great　subsidence　and　cracks　in　the　ground　surface　as　well　as　those　in　the　preliminary　support,a　double　downside　drifts　construction　method　was　presented　The　drifts　were　used　to　detect　geological　conditions　and　reinforce　the　lower　parts　of　the　tunnel　Its　construction　procedures　and　load　transiting　mechanism　were　then　described　Its　Construction　behavior　was　also　studied　by　numerical　simulation　using　software　MIDAS　The　results　show　that　(1)　double-side　drifts　can　improve　tunnel　load,the　key　construction　step　is　arch　ring　excavation　and　core　soil　is　good　to　keep　tunnel　steady;　(2)　weak　parts　mainly　l ocate　at　wall　foot　of　drifts,wall　foot　and　crown　foot　of　tunnel,and　the　connections;　(3)　reinforcement　of　soil　under　the　drifts　has　no　apparent　effect　on　improving　rock　deformation　and　support　load　Advice　on　construction　was　proposed　that　main　parts　to　be　reinforced　are　drifts　(its　foot　depth,connection　parts　with　tunnel,and　its　corners)　and　core　soil　should　be　kept　if　rock　is　unsteady　and　needs　reinforcing     

Heat Exhaust Ventilation for Ultra long GIL Tunnel（超长GIL管廊排热通风研究）

The GIL chamber in the utility tunnel under Tanxinpei Road in Wuhan is an ultra long closed structure. Heat exhaust ventilation is the controlling problem in engineering design for the project, especially the heat transfer between the tunnel and the surrounding soil in the long term. A one dimensional model for the GIL chamber is established by using the IDA tunnel simulation software to analyze the short term and long term heat exhaust, respectively. The short term heat exhaust is analyzed for the typical climate of summer/winter/transitional seasons and the long term analysis is carried out under the seasonal changes in 1 year/ 10 years/ 30 years. The short term analysis results indicate that the slope of the utility tunnel and the temperature gradient lead to lower ventilation efficiency in certain areas. The long term analysis results show that the air temperature in the GIL chamber and the wall temperature rise most pronouncedly during the first 5-6 years of operation and remain stable for the remaining time within 30 years. It also is found that around 10%-40% of the heat is released to the surrounding soil. A three dimensional model of the GIL chamber is established using the fluid mechanics based program, OpenFOAM, for 3D simulation. The effects of cables and brackets on the temperature and velocity fields in the chamber are analyzed. The effect of non uniformity of velocity distribution and the stack effect on the temperature distribution in the GIL chamber are revealed. The results can provide some reference for the design and specification revision of heat exhaust ventilation for similar utility tunnels in the future.     

Scientific and Technological Innovation and Operation related Issues for Island Tunnel of Hong Kong Zhuhai Macao Fixed Link Project（港珠澳大桥岛隧工程建设的科技创新和 运营后应关注的若干问题）

The author explains why a giant undersea immersed tube tunnel was selected for the sea area of the main channel of the east side of the Hong Kong Zhuhai Macao Fixed Link Project, instead of employing a bridge or shield tunnel; and summarizes several domestic and international leading innovative technologies applied in the island tunnel construction of the Hong Kong Zhuhai Macao Fixed Link Project, including the use of huge self stabilized steel cylinders as retaining structure of foundation pits for constructing the artificial islands, the large area and ultra deep "sand compaction pile (SCP) composite foundation" reinforcement technology, "semi rigid segment joints", "sandwich" steel RC combined inverted trapezoid closure joints, and crack control and anti corrosion/durability design for RC tube structure. All these technologies reflect Chinese wisdom and Chinese speed. The author also points out some technical issues to which attention should be paid after the immersed tube tunnel of the project is put into operation: （1） Will the post construction settlement and differential settlement of the immersed tube tunnel further develop after the project is open to traffic? How much is the final convergence value? If it exceeds the limit, what control measures should be taken?（2） How to deal with the issue that the joints of large/small elements or segments are open? How to ensure that all the large and small joints between segments of the tube are "watertight"? Furthermore, the author presents some suggestions and control measures: （1） For excessive post construction settlement (especially differential settlement) spotted on large joints, it is suggested to incorporate "micro disturbance grouting" for post treatment. （2） If a joint opens under the excessive positive bending moment at the floor slab, it is believed that the open joint on the floor slab can be closed again by cutting off some prestressed tendons in the roof slab of the segment to reduce the positive bending moment of the section.     

Design and Safety Measures of Metro Station in Flood District（行洪区地铁车站设计及安全措施研究）

The design and flood flowing safety measures of the metro station in the flood district, such as scour protection, flood control, collision prevention and floating resistance, are studied based on the flood control evaluation on the Dongzhuang Station of the Shijiazhuang Metro Line 1 Project (Phase Ⅱ). Then feasible design measures are put forward to meet the requirements of flood control evaluation during different flood return periods. The design scope for main works includes: increasing the burial depth of the station, using the retaining piles as the anti floating piles, and adopting the heightened anti flooding retaining wall and anti flooding baffle. Additionally, the civil air defense door is also used as the flood gate in case of the unelevated ground at the entrance/exit in auxiliary works. Finally, the base slab at the entrance/exit is lower than the area below the maximum scouring line, the counterweight is backfilled in the void space, and the integral rigidity of the auxiliary structure is enhanced.     

General Design of Shenzhen Zhongshan River crossing Link Project（深圳至中山跨江通道工程总体设计）

Shenzhen Zhongshan River crossing Link is the first super integrated project in the world that consists of four different types of structures, i.e. ultra long and wide immersed tunnels, super large span sea crossing bridges, deep water artificial islands and undersea interchanges. The river crossing is designed for two way and 8 lane as per highway technical standards. Based on project characteristics and its technical difficulties, engineering solutions and the associated technology innovations have been listed as follows: (1) Proposed a design concept of standardization, industrialization, intelligence and project integration, and completed the study of overall design of Shenzhen Zhongshan River Crossing Link. An immersed tunnel with a combined steel shell and concrete composite structure is designed and the width of tunnel elements is from 46 to 55.5 m; Lingdingyang Bridge has been designed as a suspension bridge with a 1 666 m main span and two 270 m high main bridge towers. For West Island, a temporary enclosure caisson structure made of ultra large steel cylinders with a diameter of 28 m is designed to achieve a rapid artificial island formation. (2) Summarized the design and construction solutions related to combined steel shell and concrete structural immersed tunnel, the mix design, batching and concrete casting methods of high strength self compacting fluidized concrete, concrete quality check and inspection, design and construction of deep cement mixed (DCM) pile foundation for immersed tunnels, design and construction of large scale undersea dimensional transport interchange, flutter and wind stability design for super large span suspension bridge with monobox girders, and key techniques related to design and construction of offshore anchorage in deep sea. Furthermore, an equipment is developed and innovated for not only transport, also for installation of immersed tunnel elements to ensure the implementation of the project in an effective and economical way.     

Research Progress and Prospect on Dynamic Response of SFT Structures(悬浮隧道结构动力响应研究进展与展望)

Construction of submerged floating tunnel （SFT） is one of the major solutions for fjord crossing projects and deep sea crossing projects in the future. Aimed to solve the key problems in SFT construction, the authors present an overview on the progress of the researches made in China and other countries in recent years on cross section of SFT, dynamic response of SFT segment structure, vortex induced vibration of anchor cable, testing technique and applicability of SFT, summarize the critical problems in the dynamic response research of SFT structures and make prospect on the trend of further SFT research. Conclusions are drawn as follow: (1) In the aspect of cross section design, SFT with ear shaped or elliptical cross section has good stability in the complex environment of flowing water, with factors comprehensively considered, such as cross section of SFT segment structures, buoyancy weight ratio and layout. (2) In the aspect of dynamic response of structures and anchor cables, the current research methods are mainly based on theoretical derivation and numerical simulation, and poorly rely on model based testing technique; therefore, it is necessary to perform model tests under combined loads from the environment, traffic and SFT, for mutual check between the theoretical analysis and numerical model. (3) In the aspect of applicability, it is necessary to build small SFT in feasible water conditions to make research on the physical SFT in the static waters, to identify problems and to lay a foundation technically for building large SFTs in the complex sea conditions.     

宁波软土地区基坑数值计算中HS模型参数试验研究

土体HS模型已成为软土基坑数值模拟中较为常用的本构模型之一,但由于其模型参数较多,很多参数无法从勘察报告中直接获取。为了解决模型参数的取值问题,选取宁波地区典型的2种土样（淤泥质土、粉质黏土）,开展标准固结试验、三轴固结排水剪切试验以及三轴固结排水加载-卸载-再加载试验,获得土体应力-应变关系。根据曲线确定宁波地区典型土层的HS模型参数Erefoed、Eref50、Erefur、c′、φ′ 和Rf,以及模型参数之间的关系。并将试验结果与上海软土地区、天津软土地区取得的模量关系进行对比分析。最后对宁波新典路过街通道深基坑工程进行三维有限元分析,计算结果与实测数据较为接近,从而验证HS 模型及试验获取的HS参数在宁波地区基坑开挖数值计算中的适用性。     

盾构井环框梁等效侧向刚度计算及对基坑的影响分析

为研究在地铁明挖基坑计算中由于忽略盾构井开孔导致的结构侧向刚度削弱问题对基坑受力和变形的影响，以武汉地铁11号线未来三路站标准2层盾构井基坑为例，建立荷载-结构模型，根据k=F/l计算盾构井环框梁结构等效侧向刚度，并将其作为基坑逆工况换撑刚度； 利用Plaxis有限元软件，建立土层-结构模型，对在基坑逆工况回筑过程中采用环框梁等效侧向刚度和整板刚度2种不同换撑的刚度进行对比分析，结果显示： 2种换撑刚度造成围护结构最大位移相差4.8%，最大弯矩相差2.7%，最大剪力相差1.3%，总体差别不大。     

浅议钻孔灌注桩施工质量问题及防治措施

结合杭州市解放路延伸工程,采用钻孔灌注桩作为基坑围护结构的实例,介绍了深基坑钻孔灌注桩施工过程中经常出现的一些质量通病及防治措施。     

紧邻地铁深基坑悬臂式挡土墙保护及基坑支护设计研究

为确保昆明轨道交通4 号线朱家村站基坑开挖及支护过程中基坑及挡土墙的安全,通过对不同深基坑支护措施及挡土墙保护方案的比选,并结合数值模拟验算结果,分析在深基坑开挖支护各工况阶段的挡土墙安全指标,选出工期短、经济性好、安全性高的挡土墙保护方案。结果表明,在挡土墙高度较小时,采用型钢斜撑结合基坑支护结构对挡土墙进行保护,安全、快捷、经济、高效, 对于以后类似条件下的紧邻深基坑挡土墙保护具有较强的参考意义。     

软土地基深基坑拉森钢板桩支护关键技术研究——以北洋泾路为例

依托上海市北洋泾路扩建工程,重点研究了软土地基深基坑采用拉森钢板桩作为基坑围护的关键技术和安全管理措施。根据工程所处的地质条件和支护方案,总结了软土地基深基坑拉森钢板桩支护施工的难点。结合支护施工方案,分析了拉森钢板桩施工的关键技术,并在此基础上提出了施工控制技术参数和相应的安全保障措施,为拉森钢板桩在软土地基深基坑支护中的应用提供借鉴与参考。     

地铁车站超宽深基坑内既有高架桥梁桩基托换关键技术研究

佛山地铁2号线换乘车站张槎站基坑宽50.3 m,深16.9 m,局部位于既有禅西大道桥下（净高仅7 m）。为解决低矮空间下超宽深基坑支护、既有高架桥桩基托换等难题,提出如下技术措施： 1)采用高桩承台桩基托换技术对位于车站中央桥桩进行托换,托换承台高于车站基坑面,基坑内支撑穿过新旧桩基形成对撑,内支撑与新旧桩相对独立; 2)地下连续墙幅宽调整为4 m,采用小型钻机成槽,以改善桥下施工工艺; 3)地下连续墙与两侧既有桩之间增加防塌孔措施; 4)基坑内支撑均采用混凝土支撑并加临时立柱以增加内支撑稳定性。以上措施解决了托换体系与车站基坑相互影响的问题,确保了低矮空间下超宽深基坑施工安全及既有桩基的安全。经数值计算论证、现场施工验证,提出的超宽深基坑内既有高架桥梁桩基托换关键技术是合理、安全、可行的。     

深厚软土地区地铁车站工程深基坑开挖施工监测控制技术研究

以杭州地铁4号线火车东站西广场地下空间连接工程(官河站)为典型案例,该工程施工难度大,安全风险高,因此,针对深厚软土地区地铁深基坑工程施工的监测及控制基坑变形工程措施进行探讨,取得了施工过程中深基坑及周边环境安全可控的效果,保障了工程的顺利进行。     

昔格达组地层大断面隧道变形特征分析

为掌握昔格达组地层大断面隧道变形特征,确保大断面隧道施工期间围岩的稳定性,以改建铁路成都至昆明线米易至攀枝花段桐梓林隧道为依托,采用数值模拟与现场多断面监测相结合的方法,研究在三台阶临时仰拱法施工中昔格达组地层大断面隧道变形的时空效应。研究结果表明： 昔格达组地层大断面隧道洞周围岩变形以竖向沉降为主;拱顶先行沉降与上台阶开挖引起的拱顶沉降之和占总沉降的41.3%,超前影响范围为1.3D;隧道开挖期间拱顶沉降和拱脚水平收敛主要受中台阶开挖的影响;隧道拱顶沉降随时间变化的预测公式为U=102.105·exp(-5.33/X);隧道拱脚水平收敛随时间变化的预测公式为L1=19.552·exp(-7.49/X);隧道墙腰水平收敛随时间变化的预测公式为L2=17.862·exp(-23.26/X)。     

深基坑承压水组合式处理措施的研究及应用

随着社会发展,基坑的开挖越来越深,如何更经济、更安全、更有效的处理基坑承压水问题越来越重要。本文结合杭州某地铁深基坑工程,对四种常见的承压水处理措施进行了分析,提出深基坑承压水组合式处理方法;并采用数值分析软件对隔水帷幕的长度进行了数值模拟分析,计算出最经济的、最合理的围护深度为63m;通过现场的抽水试验进一步验证了数值模型的合理性,试验的结果也验证了的深基坑承压水组合式处理方法的可行性;可为杭州等地区其他深基坑承压水处理提供有益的参考。     

伺服钢支撑在杭州软土基坑中的应用

随着城市发展的加快,地下空间的开发越来越受到重视,但基坑周边的环境也越来越复杂,对基坑的变形要求也更加严苛。本文以杭州地铁区间风井基坑为例,通过分析伺服钢支撑下的侧向位移变形,得出伺服钢支撑下基坑侧向变形只有预应力钢支撑下基坑侧向变形的一半,且基坑的侧向变形与钢支撑的竖向布置方式有着密切的关系;同时,通过分析伺服钢支撑与普通支撑下地表沉降数据,证明了伺服钢支撑对控制周边环境有着良好的效果,可为杭州地区同类型基坑变形控制提供参考。