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ScienceDirect Procedia Engineering 166 (2016) 53 – 60
2nd International Symposium on Submerged Floating Tunnels and Underwater Tunnel Structures
Challenge in design and construction of submerged floating tunnel and state-of-art Yiqiang Xianga,*, Ying Yang a a
Department of Civil Engineering, Zhejiang University, Hangzhou, 310058, China
Abstract Submerged Floating Tunnel (SFT) is a new type of transport structure. It is different from the general bridges and tunnels engineering, it has a significant advantage over conventional structures in crossing long, large and deep water areas. Hence, SFT has great potential for development of infrastructures in crossing straits. Aiming at features of SFT, this article discuses some challenges and problems, which are faced in design and construction of SFT, such as wave load determination, vortex-induced vibration, immigration and reduction of accidental load and situation, durability, innovational construction method, risk identification and control etc. The state-of-art and works done by Zhejiang University in the relative areas of SFT were introduced. The technological difficulties and corresponding solution were proposed. At last, the several key problems to be needed further research were proposed, so as to provide reference for the design, construction and project risk analysis of future SFT. © Published by Elsevier Ltd. This © 2016 2016The TheAuthors. Authors. Published by Elsevier Ltd. is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of SUFTUS-2016. Peer-review under responsibility of the organizing committee of SUFTUS-2016 Keywords: Submerged floating tunnel, design, construction, durability, risk analysis
1. Introduction Submerged Floating Tunnel (SFT), known as Archimedes Bridge in Italy, is a kind of innovative traffic structure, which is used to cross straits, large lakes or deep rivers [1, 2]. It generally consists of tunnel tube suspended in water, anchor cables fixing displacement of tunnel, deep water foundations and revetments connecting quayside. A typical submerged floating tunnel is shown in figure 1.
* Corresponding author. Tel.: +86-571-88208700; fax: +86-571-88208700. E-mail address:
[email protected]
1877-7058 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of SUFTUS-2016
doi:10.1016/j.proeng.2016.11.562
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Fig.1 A typical SFT
Fig.2 Coastal passages and large channels
Compared with conventional tunnel or bridge, SFT has the following special advantages [3]: (1) The longitudinal slope and total length of SFT are much shorter than that of immersed tunnel and underground tunnel. (2) SFT can achieve all-weather operation making the traffic to be smoother. (3) It has little influence on the surrounding environment, and rarely destroys local landscapes. (4) The cost of SFT per unit length has little to do with its total length, so it has more economic advantages than traditional tunnel or bridge. (5) It is convenient for laying municipal water, electric and communication pipeline across straits, lakes and rivers within SFT. At present, Taiwan Strait, Bohai Strait and Qiongzhou Strait haven’t been connected (Fig.2) in China. Complex geological and climate conditions, wide and deep waterways are the common characteristics of these three straits. It is fully of challenges to cross by bridges and tunnels. As a kind of innovative structure, though SFT is very competitive in connecting these straits, it still faces a lot of challenges and problems to be studied further compared with traditional tunnel and bridge [4, 5]. 2. Main Challenges Stability of SFT depends on the balance between dead load, moving load, buoyancy and anchoring force. Besides of those conventional loads, SFT is also subjected to environmental loads, such as the action of wave and current, which plays an important role in structure design, construction and durability. So engineers have to face new problems and challenges that have never met in the past: 1) The action of wave and current exerting on SFT produce fluid-solid coupling vibration on structure or components. Behaviour and mechanism of SFT are very complex under such actions. They are the key points and difficulties for structure analysis. 2) Because SFT remains in the marine corrosive environment, the materials of tube and anchor cables are easy to be corroded. In addition, anchor cables are vulnerable to fatigue damage under dynamic loads, which is a threat to the whole SFT structure. Therefore, it is necessary to study the durability and resistance-fatigue failure mechanism of SFT and put forward corresponding solution strategies. 3) SFT tube is generally immersed in the depth of 20-30m under water, once collision accidents or terrorist attacks happen during its operation, the consequence is more serious. Therefore, how to improve safety degree of SFT, reduce or avoid the risk of accidents, and take reasonable escape and rescue measures as soon as possible after accidents is a critical problem for ensuring SFT’s operational safety. 4) It is still a challenge to construct foundations in 50-200m deep water with complex marine geological conditions. Putting forward effective construction methods on the basis of existing construction technology is the critical issue to the safety and economic advantages of SFT. 5) There are many risks and uncertain factors exist during construction and operation. How to recognize and control these risks and uncertainties, including investment risk, design risk, construction risk, natural disasters, extreme events, operation management risk and so on, has an important theoretical meaning and engineering
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guidance. 3. Review of research status 3.1. Wave Force At present, Morison equation is mainly used to calculate the fluid force acting on SFT. Hiroshi Kunisu (1994) [6] used Morison equation and boundary element method to analyze SFT’s behaviour under wave force with different anchorage types. They thought that the wave force acting on SFT tube is mainly inertia force. Mai Jiting, etc. (2003) [7] found that SFT’s property also has effect on wave force by Morison equation and linear wave theory. The period of wave has obviously effect on the magnitude of wave force. The calculation diagram is illustrated in Figure 3. Mai Jiting, etc. (2007)[8] also calculated wave load by diffraction theory and source-sink method. She pointed out attention should be paid to the wave-current effect and the change of wave force in vertical direction. Wang Guangdi (2007)[9] used numerical simulation method to analyse flow field and pressure distribution around the surface of SFT tube with four different shapes (circle, polygon, curve shape and oval). In order to consider the changes of wave force with depth, combining with Morison equation, the author, etc (2011) proposed layered integration method to calculate horizontal and vertical wave force [10]. The calculation chart is shown in figure 4. Ș(t)
U ( y)
Fig.3 Calculation of wave force [8]
x
U ( y)
Fig.4 Layered integration method [9]
3.2. Vortex-induced Vibration Vortex-induced vibration (VIV) will be caused on SFT tube and anchor cables by the action of vortex. When the frequency of vortex is close to the natural frequency of structure or components, vibration amplitude will increase sharply because of vortex-excited resonance. As the main support components, the stability of anchor cables in wave and current is directly related to the safety of SFT. Li Jian, etc. (2006)[11] studied vortex-induced lock in velocity of anchor cables and pointed out the movement of cable is very complex. Mai Jiting, etc. (2005)[12] researched transverse vortex-induced response of tension legs in SFT under current effect. Chen Jianyun, etc. (2007)[13] established vortex-induced vibration equation of anchor cables based on Morison equation, analyzed influence of inclined angle, tension and cable length on transverse vibration. According to Hamilton principle and Morison equation, the author, etc. (2012) [14] deduced the motion differential equations of anchor cable-tube coupling system to analyze the nonlinear vibration characteristic in five typical work cases and different parameters. The results showed that: 1) The coupling vibration between cable and tube is obvious 2) The initial disturbance of SFT tube has a great influence on instantaneous amplitude of anchor cables. 3) The vortex-induced vibration of anchor cables can stimulate parametric vibration of system. 4) The stable amplitude of system depends on the size of the vortex-excited force. 5) The reasonable inclined angle of anchor cables is between 45°~ 60°. Generally, there are three kinds of methods to avoid VIV of anchor cables: 1) Choosing reasonable structure parameters. 2) Installing damping devices. 3) Using additional disturbing flow device. Chao Chunfeng (2013)[15, 16] did the experimental study on the effect of three different disturbing flow device, including spiral fringe, control rod and fairing, as shown in Figure 5. The results showed that the spiral fringe has the most obvious effect in all
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working conditions, while the effects of the control rod and fairing are related to current direction.
(a) Spiral fringe
(b) Control rod
(c) Fairing
Fig. 5 Three disturbing flow devices of anchor cables
3.3. Accidental Situation Analysis During the operation of SFT, there are various accidental situations, such as earthquake, collision caused by shipwrecks, fishing trawler and vehicles, even terrorist attacks. Though accident occurrence probability is low, the consequence is very serious. At present, the study of accidental situations mainly focuses on the earthquake. Fogazzi (2000)[17] and Di Pilato (2008)[18] developed a program to simulate fluid-structure interaction and soilstructure interaction using three-dimensional beam element. A large deformation cable element is developed and multi-supporting seismic effect of SFT is studied. Luca Martinelli, etc. (2011) [19] proposed a new method to get response spectrum based on median pseudo-acceleration response spectrum. Meanwhile, they also developed a cable element with three nodes considering fluid action, and analyzed the nonlinear seismic time history response of SFT. Xiao, etc. (2010)[20] used finite element method to study transverse seismic response of SFT with different boundary conditions of revetments, including simply- supported, fixed and elastic support. Chen Jianyun, etc. (2007)[21] studied the influence of seabed geological properties on dynamic water pressure (P-wave) of SFT with rigid cables. Sun Shengnan (2008)[22] stimulated interaction between SFT and fluid under seismic excitation and did the first experiment test to study the seismic response of SFT. Chao Chunfeng etc. (2013) derived the calculation equations and boundary conditions of SFT under the P-wave action with the help of wave equation theory. In their work, it is assumed that:1) the only rigid displacement and no elastic deformation take place in vertical plan of SFT; the dynamic effect caused by seawater and tube mass is only considered; the influence of seawater up and down the tunnel, anchor cable’s rigidity and the distance between anchor cable is also considered [23]. In addition, aiming at the problem of transverse seismic response of SFT and combining with the typical seabed geotechnical properties of the South China Sea, the author, etc (2015) used linear soil spring to simulate the restriction effect on SFT tube and adopted large mass method to analyze the transverse displacement, bending moment, torsion and cable tensions of SFT across Messina strait under the seismic action [24]. At present, there are very few researches on the dynamic response of SFT under impact loads. With equivalent mass method, Hui Lei (2008)[25] obtained local displacements and strains of tube at the impact point. Based on the law of conservation of energy in the elastic collision, Sung-il Seo, etc (2013)[26] calculated the maximum deformation and internal force of SFT which was regarded as elasticity support beam. The results were checked by finite element analysis. Yun Lee (2013)[27] adopted ANSYS LS-DANY to analyze the global and local collision response of SFT in different collision angle, got the maximum moment and displacement according to the force equilibrium equation and energy balance equation.
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3.4. Durability The chloride ion in seawater is an important factor for the corrosion of steel and concrete. For ordinary R.C structure, once the crack occurs, the chloride ion will seriously damage steel bars, reduce load bearing capacity and shorten service life. For the structures with a large investment and great social influence, the life expectancy should be 120~150 years. During the period of service, the structures must satisfy the requirements of delectability, reparability, convertibility, controllability and sustainability to meet the changes of itself and environment. Usually the service lives of component and structure are different. It is essential to ensure that component can be checked, exchanged, repaired and strengthened when its life is lower than that of the whole structure. The author, etc have done research works on the life-cycle design theory of concrete bridge and maintenance strategies based on performance in recent 10 years [28]. The mechanism of deterioration caused by carbonization, chlorine ion penetration and alkali-aggregate reaction have been relatively mature and applied in structural durability design before 2010. However, the research of the influence of deterioration mechanism on ultimate bearing capacity of concrete bridges is relatively insufficient. Especially, the coupling mechanism of environment and load is more complicated. The author did corresponding works and proposed prediction model for remaining service life of concrete bridge. These prediction models are mainly based on concrete durability failure, reliability and life cycle cost. According to these studies, corresponding maintenance strategies and methods is proposed. 4. Construction Method Besides the theoretical analysis, there must be a set of construction method to build a SFT. Because there is no existing SFT in the word, the construction methods of immersed tunnel can be taken as a reference. Main construction contents of SFT can be divided into three parts: prefabrication of tube segments, transportation and installation of tube segments, installation of anchor cables and foundation. (1) Prefabrication of tube segments Tube segments of SFT are prefabricated in dry dock. The length of each tube segment is determined by the anchor spacing and transport conditions. The internal space of tube segments consists of roadway, escape way, air convection channel, ventilating duct and so on. To ensure the internal space to be airtight, double-walled section is usually adopted, as shown in Figure 6. The complicated cross section and work conditions requirement bring some difficulties to prefabrication: (1) The accuracy of tube fabrication is high. The size of tunnel section must be strictly controlled to meet the needs of underwater connection. (2) Tube of SFT requires high waterproofness, which is mainly provided by structure itself and material. Penetrating cracks are not allowed and surface cracks should be avoided and controlled as much as possible. Thus high performance fibre reinforced concrete is recommended. (3) It is necessary to take appropriate measures to control the hydration heat of large volume concrete casting. Ventilating duct 䙊仾䚃 䱢⑇㡡 Z
Escape 䘳⭏䚃way
䘳⭏䚃 way Escape
Y
Traffic 㹼䖖䚃lane
Traffic 㹼䖖䚃lane
Fig.6 A typical SFT tube section
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(2) Transportation and installation of SFT There are two kinds of installation approaches for tube segments: floating and sinking method, incremental launching method. Floating and sinking method is similar as immersed tunnel. Incremental launching method means carrying the tube segments to inclined slide way on shore and using hydraulic jack to push them into water step by step. The in connection between tube segments by prestress tension should be finished before pushing. No matter what kinds of installation methods, when the tube segments are placed in design location, it should be anchored timely. For floating and sinking method, permanent anchor cables can be installed directly. Temporary anchor cables or buoys are also used to keep stability. When choosing the incremental launching method, the tube segments are anchored by temporary anchor cables and buoys firstly. After finishing installation, permanent anchor cables are applied. Though the similarities between SFT and immersed tunnel, there is a lot of uncertainties and risks in the construction of SFT: (1) Precise connection of tube segments is very difficult under water. It is not easy to control the tube segments posture in the wave and current environment. (2) The tube is in a stage of cantilever during construction. It is so vulnerable to bad weather, ocean currents, which will cause overall instability. (3) The sustained vibration induced by environment actions will disturb the monitoring and control of SFT alignment during construction. 5. Risk Assessment There are many risk assessment methods and each of them has different advantages, disadvantages and application scopes. Generally these methods can be roughly divided into two categories: qualitative analysis and quantitative analysis [29]. Qualitative risk analysis method depends on analysts’ insights and analytical ability. It is a kind of method for analyzing and assessing risk with the help of experience, knowledge, expertise and logical judgment. Quantitative analysis method relies on test data and statistical data. It assesses risks by establishing mathematical model and numerical simulation. Li Jing, etc. [30] identified, quantized and evaluated all kinds of risk indexes in construction phase of SFT and obtained reference indexes based on BP neural network theory. Li Jian[31] analyzed overall risk of SFT by fuzzy comprehensive evaluation method. He divided the overall risk into eight classes and obtained security risk values. The results shown risk level of SFT is moderate, which can be accepted by people. Based on the risk identification and control of bridge engineering, Xiang, etc adopted fuzzy analytical hierarchy process (FAHP) to assess the risk of SFT in the aspects of planning, design, construction, operation and investment [29, 32, 33]. Meanwhile, taking the Qiandao Lake SFT as example to analyze its environmental risk and proposed corresponding measures and suggestion [34, 35]. 6. Further Works SFT is an innovative structure that has never been existed. It is much more complex than bridge and tunnel due to its unique structure form and complicated working environment. Although SFT has a lot of advantages and great development potential, there are still some problems and challenges need further research. 1) Structure analysis method Fluid-structure interaction is the key issue in structure analysis of SFT. However, at present, many analyses for SFT are based on Morison equation, which simplifies the fluid action as hydraulic resistance and added mass force. So it is necessary to study the mechanism and influence of fluid-structure interaction. Some scholars propose flowsolid-soil interaction analysis method that can better deal with the relationship among structure, loads and constraint. 2) New material application To meet the requirements of marine environment, the materials of SFT must have the property of high strength, anti-impact toughness, crack and fatigue resistance, waterproofness and corrosion resistance. High performance concrete and steel-concrete composite structure have high strength, impermeability and great long-term performance.
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They have good application prospect in SFT. On this aspect, there are still a lot of works to do, such as corresponding design methods, construction technologies and maintenance measures. 3) Construction method Up till now, there is still no systematic research on construction method of SFT. The deep water foundation construction, large volume concrete casting, tube segments connection and anchor installation have great risks and difficulties, which should be carefully studied and treated. 4) Structural safety Reasonable measure should be proposed to keep the safety of SFT when shipwrecks, vehicles collision, explosion, fire and the fracture of anchor cables happen. 5) Monitoring Like bridge and tunnels, it is essential to monitor mechanics behaviors in SFT’s key sections. The data obtained can be guidance for design, maintenance methods, and management decisions. Taking Qiandao Lake SFT as an example, the author, etc. (2009) had studied the indexes and method for health monitor of SFT [37]. 6) Specifications of design, construction and maintenance As a new marine structure, SFT is obviously different from other traffic structures. However, at present, China doesn’t have any specifications for design, construction and maintenance for SFT. So compiling a complete set of specifications based on theoretical researches is significant for the application of SFT. Acknowledgements We gratefully acknowledge the support from the National Natural Science Foundation of China (No. 51279178) and (No. 51541810). References [1] Y. Xiang, J. Xue, Study on submerged floating tunnels in the world, Journal of China & Foreign highway, 6 (2002) 49-52. (In Chinese) [2] D. Ahrens, Submerged floating tunnels—a concept whose time has arrived, Tunnelling and Underground Space Technology, 12.2 (1997) 317-336. [3] Y. Gan, Spatial Analysis and segmental model experimental of SFT under water, Hangzhou: Doctoral Dissertation of Zhejiang University. 2003. (In Chinese) [4] Y. Xiang, Y. Yang, C. Chao, Challenges and solutions of future channels construction over straits or bays in China coastal area, Sixth Symposium on Strait Crossing, 16 – 19, June 2013, Bergen, Norway. [5] Y. Xaing, A future new traffic solutions across long waterway and deep sea- Submerged floating Tunnel and its development research suggestion, The Sixth Forum of science and technology innovation on China Highway, 2013, April 17-18. Beijing. (In Chinese) [6] H. Kunisu, S. Mizuno, Y. Mizuno, Study on submerged floating tunnel characteristics under the wave condition, The Fourth International Offshore and Polar Engineering Conference. International Society of Offshore and Polar Engineers, 1994. [7] J. Mai, B. Guan, A preliminary calculating analysis of the wave forces on a submerged floating tunnel by applying the Morison equation, Journal of Shijiazhuang Railway Institute, 16.3 (2003) 1-4. (In Chinese) [8] J. Mai, X. Yang, B. Guan, Calculations of the wave loads on submerged floating tunnels, Journal of Railway Science and Engineering, 5.4 (2007) 83-87. (In Chinese) [9] G. Wang, X. Zhou, B. Gao, Flow resistance analysis of submerged floating tunnel, Journal of Southwest Jiaotong University, 6.42 (2007) 715-719. (In Chinese) [10] Y. Xiang, K. Zhang, Calculation of wave force acting on submerged floating tunnel, Journal of Zhejiang University (Engineering Science), 8 (2011) 1399-1404. (In Chinese) [11] J. Li, Y. Li, Analytical solution to the vortex-excited vibration of tether in the Submerged Floating Tunnel. Geo Shanghai International Conference, Shanghai, June 6-8, 2006, pp. 147-153. [12] J. Mai, Z. Luo, B. Guan, The vortex-excited dynamic response for a submerged floating tunnel under the combined wave and current effect, Journal of the China Railway Society, 27.1 (2005) 102-105. (In Chinese) [13] J. Chen, B. Wang, S. Sun, Analysis of vortex-induced dynamic response for the anchor cable of submerged floating tunnel, Engineering Mechanics, 2007.10, 10(24):186-192. (In Chinese) [14] Y. Xiang, C. Chao, Vortex-induced dynamic response analysis for the submerged floating tunnel system under the effect of currents. Journal of Waterway, Port, Coastal, and Ocean Engineering, 139.3 (2013) 183-189. [15] Y. Xiang, C. Chao, VIV and control in submerged floating tunnel’s cables, Proceeding of International Conference on Vibration Problems (ICOVP-2013), Lisbon, Portugal, Sep. 9-12, 2013ˈISBN:978-989-96264-4-7.
59
60
Yiqiang Xiang and Ying Yang / Procedia Engineering 166 (2016) 53 – 60 [16] C. Chao, Dynamic Response Analysis and Experiment of Submerged Floating Tunnel based on Fluid-Structure Interaction. Hangzhou: Doctoral Dissertation of Zhejiang University. 2013.9. (In Chinese) [17] P. Fogazzi, F. Perotti. The dynamic response of seabed anchored floating tunnels under seismic excitation, Earthquake Engineering and Structural Dynamics, 29(2000) 273–95. [18] Di Pilato M, F. Perotti, P. Fogazzi, 3D dynamic response of submerged floating tunnels under seismic and hydrodynamic excitation. Engineering Structures, 30.1 (2008) 268–281. [19] L. Martinelli, G. Barbella, A. Feriani, A numerical procedure for simulating the multi-support seismic response of submerged floating tunnels anchored by cables. Engineering Structures, 33.10 (2011) 2850-2860 [20] J. Xiao, G. Huang, Transverse earthquake response and design analysis of submerged floating tunnels with various shore connections, Procedia Engineering, 4 (2010) 233–242. [21] J. Chen, S. Sun, The effect of seabed geotechnical properties on hydrodynamic pressure on submerged floating tunnel-P Wave, Progress in Natural Science, 1(2007) 013. (in Chinese) [22] S. Sun, Dynamic response analysis of submerged floating tunnel, Dalian university of technology, Dalian, 2008. (in Chinese) [23] C. Chao, Y. Xiang, Hydrodynamic load on SFT tube in ideal fluid layer under the action of earthquake P-wave. Acta Oceanologica Sinica, 35.5 (2013) 156-161. (in Chinese) [24] Y. Xiang, C. Chao, Transverse seismic response analysis of submerged floating tunnel considering boundary soil property, Proceedings of International Conference on Engineering Vibration, Ljubljana, Slovenia, Sep. 7-11, 2015. [25] L. Hui, F. Ge, Y. Hong, Calculation model and numerical simulation of submerged floating tunnel subjected to impact load, Engineering Mechanics, 2.25 (2008) 209-213. (in Chinese) [26] S. Seo, H. Jeong, M. Sagong, Simplified collision analysis method for submerged floating railway using theory of beam with elastic foundation, Sixth Symposium on Strait Crossing, Bergen, Norway, Jun. 16 – 19, 2013. [27] Y. Lee, S. Han, W. Park, Impact analysis of submerged floating tunnel for conceptual design, Sixth Symposium on Strait Crossing, Bergen, Norway, Jun. 16 – 19, 2013. [28] Y. Xiang, Q. Wu, Maintenance strategy and method of performance-based concrete bridges in life cycle, Journal of Chongqing Jiaotong University, 32.5 (2013) 918-925. (in Chinese) [29] T. Zhang, Study on Risk Assessment System, Method and Application of Lingjiang Bridge. Hangzhou: Master's degree thesis of Zhejiang University, 2010. (in Chinese) [30] J. Li, X. Lin, BP neural network model on risk analysis of floating tunnel construction, Construction Management Modernization, 21.1 (2007) 40-42. (in Chinese) [31] J. Li, Fuzzy synthetic evaluation on risk of submerged floating tunnel, Chinese Journal of Underground Space and Engineering, 4.2 (2008) 383-386. (in Chinese) [32] Y. Xiang, Q. Wu, T. Zhang, The risk assessment of bridge design based on the AHP-FCE model, China Civil Engineering Journal, Z2 (2010) 275-280. (in Chinese) [33] Y. Xiang, T. Zhang, Analysis and control of ship collision probability risk of Lin River Bridge, Proceedings of the international symposium on ship bridge collision and its protection, 2014.3, Beijing, China Railway Press [34] Y. Xiang, C. Liu, K. Zhang, Risk analysis and management of submerged floating tunnel and its application, Procedia Engineering, 4(2010) 107-116. [35] Y. Xiang, C. Liu, C. Chao, Risk analysis and assessment of public safety of submerged floating tunnel, Procedia Engineering, 4 (2010) 117-125. [36] Y. Xiang, Y. Yang, Some key problems of high performance fiber reinforced concrete submerged floating tunnel, Proceedings of 13th international symposium on structural engineering(ISSE-13), Hefei, China ,Oct. 24-27, 2014. [37] Y. Xiang, K. Zhang, C. Chao, A. Fiorentino, F. Mazzolani, Health Monitoring System of Submerged Floating Tunnel Prototype in Qiandao Lake, The 4th International Symposium on Lifetime Engineering of Civil Infrastructure, ChangSha ,2009, pp.471-477.
