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.     

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.     

Comparison and Selection of Ventilation Schemes for Zhagaliang Extra long Highway Tunnel（扎尕梁特长公路隧道通风方案比选研究）

In order to select a suitable ventilation scheme for a single tube extra long highway tunnel with two way traffic, as well as to solve problems in smoke exhaust and personnel evacuation in such tunnel, 3 ventilation schemes are proposed. According to the characteristics of Zhagaliang extra long highway tunnel, the 3 ventilation schemes include confluent ventilation with exhaust shaft and longitudinal ventilation with jet fans, parallel pilot tunnel forced ventilation network, and longitudinal ventilation with jet fans and sectional smoke exhaust by inclined shaft. The ventilation schemes are compared from several aspects, i.e. civil construction cost, initial investment of mechanical and electrical equipment, electricity cost during tunnel operation, ventilation control, stability of ventilation network, applicability, management and maintenance. Finally, the most suitable ventilation scheme is selected by comparing the advantages and disadvantages of each scheme, i.e. longitudinal ventilation with jet fans and sectional smoke exhaust by inclined shaft. Under the normal operation condition of the tunnel, longitudinal ventilation with jet fans is adopted in the main tunnel, and on demand ventilation can be realized. Smoke can be exhausted by inclined shaft in case of fire, which can solve the problem of smoke exhaust only in two sections by the parallel pilot tunnel. The parallel pilot tunnel can also be used for personnel evacuation and rescue.     

Reflections on Construction of Bohai Bay Crossing Corridor（对兴建渤海海峡跨海通道有关问题的思考）

The author discusses the necessity and urgency of constructing the Bohai Bay Crossing Corridor from the following aspects such as the increasing traffic volume, the convenience of the transportation after the corridor is constructed, and the regional benefit brought by the corridor. As for the timing of the construction of the sea crossing corridor, the author thinks that as long as the national economic situation permits and relevant conditions are basically available, the preliminary work should be carried out as soon as possible so as to promote the early commencement of the construction. Regarding the proposal of building another coastal national highway/high speed railway along the Bohai Bay coast, the author puts forward his viewpoints. In the aspect of construction risks, the author thinks that the geological risks in the construction of the Bohai Bay Crossing Corridor are very difficult to be dealt with; therefore, strict and detailed risk assessment should be carried out, and effective safety measures should be taken to mitigate the risks. The author also briefly describes the technological advantages of the tunnel proposal selected for the Bohai Bay Crossing Corridor, and briefly analyzes some key technological issues in the tunnel construction. The author describes the construction scheme and construction period estimation for the sea crossing corridor in details. The author makes the following proposal are given: (1)the hard rock tunnel boring machine (TBM) assisted by the drilling and blasting method should be used for the construction of the long sea crossing tunnel of Bohai Bay Crossing Corridor; (2) a parallel service tunnel shall be arranged between the twin main tunnel tubes; (3) in Proposal 2, the diameters of the twin main tunnel tubes and the service tunnel should be 8.0 m and 55 m, respectively. The proposal has two optional solutions: Solution 1: The service tunnel ( 55 m) located between the main tunnel tubes will be constructed first; for the main tunnel tubes, the disassembled TBMs ( 8 m) and the backup gantries are assembled for tunneling after arriving at the main tunnel tubes through the service tunnel and the cross passage; Solution 2 (alternative): Tunneling with  55 m TBM is carried out; the  55 m TBM will be dismantled to pass through the cross passage, and then be re assembled after arriving at the main tunnel; the start section (180 m) of main tunnel tube will be formed by  55 m TBM before it is enlarged to  8 m by drilling and blasting method; or the cross passage is enlarged to a large curved space to allow the 5.5 m TBM passing throught without disassembly. Comparison and contrast will be made and the preferred solution will be adopted. According to the rough estimation on the construction period of the 125 km long sea crossing tunnel, the total construction period of "completed tunnel" will be about 19 years (including 5 years of detailed offshore investigation) in Solution 1.     

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.     

Design Standard for Thermal Insulation and Drainage Facilities of Railway Tunnels in Cold Regions（寒区铁路隧道保温排水设施设计标准研究）

Targeted to the issue of lacking of systematic design standards for thermal insulation and drainage facilities of railway tunnels in cold regions, the authors propose the method of design division of railway tunnels in cold regions based on the division of cold regions, the current technical status of thermal insulation and drainage in tunnels, and the investigation on some tunnel freezing damage cases in northeastern China and the northern part of North China. Through analyzing the application conditions of the thermal insulation and drainage facilities and combining the measured temperatures in the operating tunnels and drainage facilities, the authors propose the suggested length for the thermal insulation and drainage facilities of tunnels in cold regions in different divisions. The results show that: (1)railway tunnels in cold regions may be classified into 5 divisions based on annual average temperature and average temperature in the coldest month; (2)the elevated thermal insulation ditch only adapts to the cold regions with a higher temperature; (3)an effective measure for thermal insulation and drainage in cold regions is to embed ditches into structures within a certain range from the portal; (4)the ditches may be arranged in structures for the trunk section of long tunnels equipped with thermal insulation measures; (5)for the tunnels with the necessary conditions available, the double spur grade and a steep gradient in the longitudinal slope may be applied, which is beneficial to improving drainage conditions and preventing the ditch from freezing.     

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.     

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.     

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.     

Key Technology of Overlength Pressure Tunnel in Water Supply Project in Central City of Jilin Province（吉林引松工程超长有压隧洞关键技术）

Water Supply Project in the Central City of Jilin Province is a large scale project which involves complex geological condition and high technical difficulties. In order to maximize the water delivery, the overlength pressure hydraulic tunnel is introduced. Based on detailed geological survey and other reliable technical references, this project can be treated as a demonstration in terms of how to lay large diameter TBM through a karst area with limestone. The in situ test is introduced to test the non bonded pre stress circumferential anchor tunnel structure and culvert structure when the water transmission engineering line crosses the shallow buried valley section. The Class Ⅰ and Class Ⅱ granite tunnels excavated by TBM is not aligned with saving project investment and speeding up construction progress. The BQ method is introduced to analyze the rock quality classification of long tunnels. There are not many domestic engineering examples of the above mentioned key technologies, and there are no mature theories and experiences to refer to. Based on theoretical research, numerical calculations, model tests, and productive in situ tests, those key technical problems of ultra long and pressurized tunnels are solved. This project has a great theoretical and engineering value.     

Analysis of Adaptability of TBM in Trial Boring Stage of Super long Tunnel（超特长隧洞TBM集群试掘进阶段适应性分析）

The total length of the 2nd stage water transfer project in the northern area of Xinjiang of China is 540 km. The project consists of three tunnels, namely Xi Er (XE) Tunnel, Ka Shuang (KS) Tunnel and Shuang San (SS)〖HJ6.5mm〗 Tunnel, with lengths of 139.04 km, 283.27 km and 92.15 km respectively. All of these three tunnels have deep cover and are super long tunnels, and 95.6% of the total length of these three tunnels is constructed by TBMs. KS Tunnel is the longest water tunnel built or under construction in the world. In the paper, the trial TBM boring scheme and schedule of the water transfer project are introduced; the geological conditions revealed are statistically analyzed; and main project difficulties, i.e. durability of key equipment in long distance driving, passing through fault and fracture zones, water inrush, single head ventilation and transportation in long distance tunneling, anti slope drainage, and rock breaking efficiency and boring efficiency, are put forward. The adaptability of the TBMs used is analyzed from the aspects of adaptability to different surrounding rocks, adaptability to bad geological conditions and countermeasures, long distance ventilation and belt conveyor mucking and countermeasures, and TBM boring stability (such as equipment availability, boring time proportion, system malfunction and operation time). The following conclusions are obtained: (1) Accurate geological survey is the precondition of efficient tunneling. (2) The open type TBM can better adapt to Grade Ⅱ and Ⅲ of surrounding rocks, jointed and fractured zones and small faults; the adaptability of the TBMs used to the large scale fault fracture zones and water rich strata in this project is poor, and it needs to be improved in aspects of TBM equipment, supporting and construction technology. (3) The average availability of the TBM equipment in the trial boring stage is 89.9%, however, the malfunction rate of some ancillary equipment is high, particularly oil leakages occur to the main bearing seals; in order to achieve long distance tunneling, it is necessary to further improve the reliability and durability of the TBM equipment. (4) The average net boring efficiency in the trial boring stage is 296%, and TBM1 in Section Ⅱ of SS Tunnel achieves up to 45.2 % net boring efficiency; and highest monthly progress rate is 1 280 m, which created the highest record of the open type TBM boring in China. (5) TBM need to make great efforts to achieve 90% of the equipment system′s availability and over 40% of the tunneling efficiency.     

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.     

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.     

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.     

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.     

Application Technology of Spray applied Waterproofing in  Unloading Tunnel of an LNG Receiving Terminal（液化天然气接收站LNG工艺隧道喷膜防水应用技术）

The application of a spray applied waterproof membrane in the case of the liquefied natural gas (LNG) unloading line tunnel constructed via the New Austrian Tunneling Method (NATM) is described. The waterproof standards for the LNG unloading line tunnel are stricter than those for regular tunnels based on the consideration of safety and environmental protection during operation. A double layer waterproofing system including radial grouting, systematic drainage facilities, an EVA sheet membrane, a spray applied acrylate waterproof membrane and other waterproofing and drainage facilities are designed based upon comparisons among several possible waterproofing solutions. The application results and consequential observations prove that the outcome of this waterproof system is satisfactory. The important issues for the successful application of the sprayed membrane in this case are summarized, including a reasonable design for the waterproofing system, performance of the sprayed membrane, proper training for the operators, adequate preparations, careful execution, and complete quality control and acceptance. The successful application of the spray applied acrylate waterproof membrane combined with other waterproofing and drainage facilities in this case has been demonstrated according to the inspection results and provides alternative solutions to improve the waterproof quality of similar tunnels under high standards.     

Innovation and Future Application of Mechanized and Intelligentized Construction Technology for High speed Railway Tunnels: A CaseStudy of Hubei Section on Zhengzhou Wanzhou High speed Railway（高速铁路隧道机械化修建技术创新与智能化建造展望——以郑万高速铁路湖北段为例）

To ensure the safe, rapid and high quality construction of Zhengzhou Wanzhou High speed Railway, a series of exploration and innovation of construction technology, structural design and information management under the condition of large scale mechanization is used in the whole construction process. The technology includes: （1）A set of advanced geological prediction, advanced pre reinforcement technology of excavation face, mechanized construction technology of primary support, wide waterproof board trolley operation technology and intelligentized full face lining trolley of large scale mechanized construction technology are formed. （2）A classification method of surrounding rock stability is established based on the mechanized construction technology, and the design parameters of the tunnel support structure are optimized under the guidance of New Austria Tunneling Method. （3）To realize informatized management of tunnel construction, the tunnel construction management system, construction information record system, construction safety management system, quality management system of concrete mixing station and quality credit evaluation system are established. Finally, on the basis of mechanized and informatized construction, exploration and outlook of the tunnel intelligentized construction technology are given from the aspects of the dynamic intelligentized design system of tunnel support system, the intelligentized robot construction technology of tunnel support system and the intelligentized monitoring system of tunnel structure, to promote China′s tunnel construction technology.     

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.     

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.     

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.