Construction Technologies for Tunnels in Special and  Complicated Geology of Lanzhou Chongqing Railway（兰渝铁路特殊复杂地质隧道修建技术）

Lanzhou Chongqing Railway is located in the uplift margin of the Tibetan Plateau, where the geological environment is very complicated and special. Based on numerical analysis and field tests, the physical and mechanical properties, micro structure, and complicated water related stability of the Tertiary sandstone are studied. A comprehensive dewatering system integrating deep surface wells and vacuum light well points in tunnel is used and the construction technique featured with advance reinforcement by horizontal jet grouting for the full face of aquiferous silty fine sand tunnels is invented to solve the problem of the Tertiary quick sand. In addition, the classification method for deformation potentiality in design and dynamic adjustment in construction of tunnels in high geostress soft rock is established, the deformation control technology combining active stress release and passive control according to the deformation mechanism is developed, an automatic real time monitoring system for operation is invented, and a complete technological system of design, construction, and operation management of soft rock tunnels is built. Moreover, the TBM equipment parameter design principles are put forward, the parallel lining and multi stage belt conveyor mucking system is researched, the phased ventilation technology is invented and thus the problem of safe and fast long distance construction by large diameter TBMs is solved. The technological achievements have filled in gaps and facilitated development of the tunnel construction technology.     

Key Technology of Sea crossing Interval Tunnel in Complex  Environment Design of Xiamen Rail Transit Line 3（厦门轨道交通3号线复杂环境过海区间隧道设计关键技术）

A sea crossing tunnel is generally large in scale, having a complex site environment, and lack of engineering experience. The success of the project is directly related to the design plan. At present, no metro sea crossing tunnel havd been built in mainland, and the design standard and technology of the sea crossing tunnel are not studied throughly. The key technology of long and large sea crossing metro tunnel design, including construction method selection, cross section design, waterproofing and drainage system design, response to complex environment in sea area, durability design, ventilation and evacuation are analyzd with methods of geological analysis, engineering analogy and comprehensive comparison based on the sea crossing tunnel of Xiamen Rail Transit Line 3. A combination of shield and mining methods is proposed for the geological conditions of different sections. The drainage system of the mining section can be maintained by applying advanced grouting to control displacement. The complex geology of the sea area is considered in the targeted design, including a deep weathering trough, a water rich sand layer, a hard rock and uneven stratum, and the development of solitary rocks. The durability design of the tunnel structure and the limit of the bearing capacity are treated equally to consider safety reserve. The tunnel adopts sectioned longitudinal ventilation and smoke extraction mode, and contains ventilation shafts and civil smoke extraction air shafts on shore to prevent disasters. The conclusions can provide technical support for tunnel scheme decision and reference for similar projects.     

Achievements and Challenges of Tunneling Technology in China over Past 40 Years（中国隧道工程技术发展40年）

In this paper, the current situation of tunnel engineering in China is introduced, especially the achievements obtained in the field of tunnel construction since the reform and opening up over 40 years. The 34 708 km long traffic tunnel built after reform and opening up takes 96% of the total length. The challenges met and achievements obtained during the key tunnel projects construction in China are presented emphatically from the aspects of extra long tunnel, deep tunnel, large tunnel, tunnel at high altitude and tunnel in complex environment. It is pointed out that: the main technological challenges during extra long tunnel construction are the accuracy of geological investigation, rapid construction and running disaster prevention; the main challenges during deep tunnel construction are high geostress, high waterpressure and high geothermal; the large tunnel faces high design and construction challenges; the challenges during tunnel construction at high altitude are freezing thawing and hypoxia; but still, many tunnels have been built under complex environments, including karst, gas, high geostress, high waterpressure, expansive rock, etc., and many technological breakthroughs have been achieved. The development trend of tunnel projects in China is proposed from the aspects of investigation, design, construction and operation, turning the development speed into development quality. It is generally acknowledged that the tunnel engineering achievements in China over the past 40 years benefit significantly from the development of international tunnel technology. Meanwhile, the development of tunneling technology in China has also greatly contributed to the international tunnel engineering development.     

Development and Thinking of Tunnels and Underground Engineering in China in Recent 2 Years （From 2017 to 2018）（近2年我国隧道及地下工程发展与思考（2017—2018年））

The author gives an overview of the development of tunnels and underground engineering in China in the past two years, including railway tunnel, high speed railway tunnel, highway tunnel, metro tunnel, hydraulic tunnel and utility tunnel, and introduces some key and representative railway, highway and municipal tunnels projects, i.e. Muzhailing Tunnel on Lanzhou Chongqing Railway, Dangjinshan Tunnel on Dunhuang Golmud Railway, immersed tunnel of Hong Kong Zhuhai Macao Bridge, China Laos Railway Tunnel, Gaoligongshan Tunnel on Dali Ruili Railway, Yuelongmen Tunnel on Chengdu Lanzhou Railway, Tianshan Shengli Tunnel on Urumchi Yuli County High speed Railway, Shenzhen Zhongshan Passage, Su′ai Tunnel in Shantou, Ka Shuang Tunnel of Ertix River Water Diversion Project, Qianhai underground integrated hub in Shenzhen and underground integrated structure of Optics Valley Square in Wuhan. The author also introduces the development and progress in the fields of engineering investigation technology, BIM technology, mechanized and intelligent tunnel construction technology, shield/TBM manufacturing and remanufacturing technology, offshore immersed tube tunnel construction technology, non circular shield tunnel construction technology, tunnel big data platform construction technology, etc. According to the operation of series national strategies and planning such as Sichuan Tibet Railway, coordinated development of Beijing, Tianjin and Hebei, the Yangtze Economic belt, and the Guangdong Hong Kong Macao Greater Bay Area, following technical demands are proposed, namely, sea crossing tunnels, construction of complex and long distance tunnels, environmental protection technology for tunnel construction in ecologically vulnerable areas, development of large scale urban underground complexes, research and development of new materials in alpine environment, intelligent diagnosis of tunnel diseases and rapid repairs, intelligent disaster prevention of ultra long complicated tunnels and underground engineering, etc. Some thoughts and suggestions are put forward in two aspects of engineering construction management mode and mechanization supporting in combination with the development status of the industry.     

Fully Prefabricated Assembling Technology of Tsinghuayuan  Tunnel in Beijing Zhangjiakou High speed Railway（京张高铁清华园隧道轨下结构预制拼装技术）

Tsinghuayuan Tunnel of Beijing Zhangjiakou High speed Railway is the first fully prefabricated high speed railway tunnel in China. The supporting structure, subrail structure, and subsidiary structure of Tsinghuayuan Tunnel are all prefabricated in the factory. The strength, deformation and stability of subrail structure are analyzed by numerical simulation method; a kind of three block type of subrail prefabricated structure is put forward according to prefabricated assembling technology; and the subrail space is used to ventilate and rescue under the stability condition. The connection between subrail structure and shield segment is the key to fully prefabricated assembling technology. By introducing the grouting technology and construction keys of subrail structure, the stress on subrail structure and shield segment can be balanced. The results can provide reference for similar projects in the future.     

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.     

Design and Application of Double shield TBMs  for Urban Metro Tunnels（城市地铁双护盾TBM设计及应用）

With reference to the construction conditions and features of metro tunnels, the design features of double shield TBMs are analyzed and key issues to be considered and settled when a double shield TBMs is used for metro tunnel construction are proposed. The issues include cutterhead′s rock breaking capacity, small curve excavation, selection of backfill grouting technology and jamming prevention and release function in fault and fracture zone, etc., which all have a direct effect on the geological adaptability, tunnel lining quality and tunneling performance of double shield TBMs. Subsequently, the specific design and optimization scheme, which includes the design of cutterhead thick steel plates, tapered shield, monorail hoist and pea gravel backfill and cement slurry grouting, etc., are studied. The success of double shield TBMs in Shenzhen Metro project well proved its remarkable geological adaptability and advantages in efficient mechanized construction.     

Study of Tunneling Technology in Tertiary Sandy Mudstone Strata with Rich Water under High Pressure: Case Study of Shuangfeng Tunnel of Mudanjiang Suifenhe Railway（第三系高压富水砂泥岩地层隧道技术研究——以牡绥铁路双丰隧道为例）

In order to deal with the technical problems of Shuangfeng Tunnel passing through water rich Tertiary sandy mudstone strata with long distance and big overburden, such as dewatering, advance reinforcement, structural design and construction method etc., reducing tunnel deformation, preventing water inrush, gushing mud and tunnel collapse, the technical route of "stereo exploration, pressure reduction by water releasing, pre grouting, supporting timely, overall monitoring" is established after the field test and data analysis. Methods of full dimensional exploration and water pressure reducing are proposed, which form the preceding reinforcing technology that are different between inside the excavation contour and outside the excavation contour. Support linings are constructed immediately after excavation of upper bench. Safety performance of tunnel structure is evaluated according to the monitoring results. The research is conducted based on Shuangfeng Tunnel and the study results are applied in the construction of the tunnel. Results indicate that it can make sense to control deformation and ensure safety by using methods of reducing pressure through full dimensional water release, adopting advance reinforcement measures that are different between inside the excavation contour and outside the excavation contour, proposing mini bench method during tunnel construction and supporting timely after excavation for tunnels passing through water rich Tertiary sandy mudstone strata.     

Innovation and Practice of Hard Rock TBM in China（我国硬岩掘进机的创新与实践）

In recent years, with the help of good national policy support, the design, manufacturing and construction technology for tunnel boring machine (TBM) in China have been greatly improved; but compared with foreign relatively proven technology, there is still a certain gap for domestic technology development and engineering application. Based on the situation analysis of research and application of TBM in China and abroad, the research work for TBM design is carried out according to the complex geological conditions of Gaoligongshan Tunnel on Dali Ruili Railway as follows. (1) The prototype disc cutter rock breaking and scaled disc cutter wearing experiment are carried out to provide reference for adaptable design of TBM cutterhead and key parameter calculation. (2) The TBM design scheme is discussed from the aspects of high efficiency rock breaking of cutters and cutterhead, TBM over excavation, integrated support system, etc. (3) Two kinds of advanced geological prediction technology, i.e. HSP method and RTP method, are researched. The study results can provide reference for design and manufacture of TBM with high adaptability in complex geology and construction application in Gaoligongshan Tunnel.     

Study of Collaborative Management of Intelligent Highway Tunnel（智慧公路隧道协同管理研究）

Aiming to solve the problems of collaborative management of intelligent tunnel and tunnel management under different traffic conditions, the tunnel is regarded as a part of highway, and five features of the intelligence are proposed from the definition of intelligence. In order to realize a collaborative management of intelligent highway tunnel, the spatial extent of tunnel is defined at first. Then, a collaborative management road topology based on road critical nodes is proposed; and a holographic collaborative control information system based on tunnel structure, facilities, vehicle, operation, management, and environment is established. Finally, collaborative control of people, cars, roads and environment could be realized, so as to improve the management level of the intelligent highway tunnels.     

盾构隧道结构耐久性问题思考

Structural durability of shield tunnel lining is a trans scale problem from mesoscopic material to macroscopic structure. With increasing amount of shield tunnel construction in China, the issues related to structural durability become more prominent. In this paper, the typical applications of shield tunnel lining in China and other countries are introduced. The service conditions and diseases of shield tunnel lining structure are then analyzed. The factors affecting the structural durability of shield tunnel lining, such as material, design, environment, construction, management and maintenance, are summarized. The research results and progress related to structural durability of shield tunnel lining are then reviewed in terms of tunnel durability, durability evaluation and prediction, durability ensuring techniques. Finally, the existing problems and future research directions in structural durability of shield tunnel lining are discussed in terms of durability ensuring techniques, impact of diseases and accidents, tunnel evaluation and rehabilitation, arrangement of secondary lining and establishment of dynamic evaluation system for structural durability.     

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.     

State of art and Prospectives of Urban Utility Tunnels in China（我国城市综合管廊建设发展现状与未来发展趋势）

Based on the introduction of the history and typical projects, the state of art of urban utility tunnels in China are mainly discussed in terms of construction mode, planning and design, construction and operation management. Then the significant technologies used for utility tunnels in China such as the green construction concept, intensive planning/design concept, intensive planning/design method, formwork slipping technology, precast/assembly technology and BIM based intelligent management technology and so on are elaborated. Finally, prospectives of utility tunnels in China are presented.     

Key Design Technologies for Cutter Replacing of Super large  Slurry Shield under Atmaspheric condition: Case Studies of Shantou Gulf Tunnel and Shenzhen Chunfeng Tunnel（超大直径泥水盾构常压换刀设计关键技术——以汕头海湾隧道及深圳春风隧道为例）

By analyzing the application cases of super large diameter shield machine in the world and taking China Shantou Gulf Tunnel and Shenzhen Chunfeng Tunnel construction for examples, the problems encountered in the research and development and construction are proposed and the key technologies to solve a series of problems, such as cutterhead maintenance and cutter changing technology under high soil and water pressure, boring in long fractured zone, are explored. More specifically, the technologies mainly involve cutterhead design, atmospheric cutter changing, main drive with telescopic and swinging function, reliable sealing system, anti blockage technique by applying double crushers, which are of great significance to the development and application of super large diameter shield machine.     

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.     

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.     

Study of Engineering Geological Conditions and Railway Tunnel Scheme across Qiongzhou Strait（琼州海峡工程地质条件及铁路隧道方案研究）

The cross sea channel for the Qiongzhou Strait not only provides a solution for transportation, but also plays an important role in the political and economic development of the region. In addition, the project has an extensive impact on many fields, such as energy, national defense, science and technology, opening up and reform, comprehensive utilization and so on. It is a significant project to enhance China′s comprehensive national strength, defend the country′s territorial integrity and promote regional economic development. The geological conditions across the Qiongzhou Strait are complex. A large amount of existing engineering geological information and hydrogeological data are collected, based on which the seismic impact on subsea tunnels and the main geological conditions including tectonic structures are analyzed. Different options crossing the Qiongzhou Strait have been considered and compared in terms of engineering geology, environmental condition, as well as the construction feasibility. The analystical results indicate that a subsea tunnel has more advantages over a bridge. Because more complicated technical difficulties have to be solved for a highway tunnel which would potentially increase construction and operation costs, a railway tunnel scheme is recommended. Vehicles can be carried by trains through the Qiongzhou Strait railway tunnel. Based on the seabed topography and geological conditions, four preliminary railway tunnel routes are proposed. After a comprehensive comparative analysis, the railway tunnel route Ⅱ is identified to be superior to other alternatives and should be the basis for determining the final tunnel layout. The proposed tunnel cross section includes two railway tunnels and one service tunnel. All the three tunnels have the same structural form and dimension and will be constructed by shield.     

Challenges and Countermeasures in Construction of  Gaoligongshan Tunnel of Dali Ruili Railway（大瑞铁路高黎贡山隧道施工挑战与对策）

In order to resolve the challenges encountered in the construction of Gaoligongshan Tunnel such as soft rock deformation of inclined shafts, water drainage and protection of vertical shafts, TBM jam in crossing areas with adverse geology, solutions and key construction techniques are developed through theoretical analysis, field test, scheme optimization and staged review and summary. The performance results of field practice show that: (1)the goal of no damages and no replacement of the primary support can be achieved by adopting the comprehensive deformation prevention technique of "ring support early formation and quick closure", setting of proper excavation line curvature, and reinforcing of support; (2)the risk of vertical shaft flooding during construction in water rich weak granite can be greatly reduced by adopting the water control principle of "exploration for any excavation, plugging as the main method, and supplemented with drainage method" and the key pre grouting technique of S shaped deep boreholes; (3)the open type TBM can quickly and safely pass through the unfavorable mylonitic granite stratum by adopting the small pilot tunnel construction method, thus the fast and high efficiency construction performance of TBM can be fully utilized.     

Some Key Technical Issues on Construction of Ultra long Deep buried Water Conveyance Tunnel under Complex Geological Conditions（复杂地质条件下跨流域调水超长深埋隧洞建设需研究的关键技术问题）

For the water conveyance tunnels in the long distance water diversion projects constructed or planned in China, most of them have to pass through mountain areas with complex geological conditions, due to the constraints of route selection. These tunnels might face engineering problems such as harsh natural environment, high seismic intensity and steep terrain, leading to difficulties in construction and high operational risks. In this paper, some key technical issues on the construction of ultra long deep buried water conveyance tunnels under complex geological conditions are summarized into 5 aspects, namely, (1) exploration and testing techniques for deep buried tunnels, (2) prediction and prevention for large deformation and rock burst in the surrounding rock masses, (3) failure mechanism and anti faulting techniques of the surrounding rock masses and lining for tunnels crossing active faults, (4) synergistic load bearing mechanism and life cycle design theory for rock support system of deep buried tunnels, (5) disaster treatment for deep and long tunnels such as prevention of high pressure water inrush. The scientific and technical problems to be solved and their development directions are pointed out, which can provide some reference for engineering construction of ultra long deep buried tunnels.     

Key Construction Technologies for Overlapping Twisted Shield bored Tunnels in Weak Water rich Strata(富水软弱地层中麻花型盾构隧道群施工关键技术)

The project under study is an overlapping twisted shield bored tunnels in weak water rich strata. The purpose of the study is to solve the key technological problems in the construction of the project. The optimal construction sequence of the overlapping twisted shield tunnels is determined according to the engineering geological conditions, the surrounding working environment, and theoretical analysis on the spatial relationship of the four tunnels, and verification control are carried out via monitoring means. The tunnel construction is properly timed, smart self propelled movable support jumbo is adopted, and grouting reinforcement technology is used to ensure the construction safety of the overlapping twisted shield bored tunnels. The grouting pre reinforcement technology and the clay shock technology are adopted to ensure the safety of the surrounding buildings. The technologies for the construction of the overlapping twisted shield bored tunnels described in this paper is of great significance for the construction of similar overlapping tunnels with high shield launching/receiving risks and crossing under important structures with small clearance.