Numerical studies for the thermal regime of a high-speed railway tunnel considering piston action on seasonally frozen regions

Author(s):  
Haiqiang Jiang ◽  
Fujun Niu ◽  
Wangtao Jiang ◽  
Li Cheng ◽  
Yongdong Li ◽  
...  

Abstract piston action describes the phenomenon that air at the train nose is pushed forward by the increased pressure and air at the train rear is drawn forward by the decreased pressure when a train passes through a tunnel. The changes of pressure can affect the thermal environment inside the tunnel, and further cause frost damage. In this paper, a fluid-thermal-solid coupled numerical model considering piston action is developed. A high-speed railway tunnel in the northeast of China is taken as an example to explore the temperature distribution laws with computational fluid dynamic (CFD). Afterwards, the effects of air temperature and train velocity on temperature distribution are analyzed. The results show that the piston action can enhance the heat transfer between cold air outside the tunnel and tunnel structure, and can cause more serious frost damage especially at the entrance and exit. The temperature distribution is characterized by three zones, including disturbed zones at two sides of tunnel and undisturbed zone at tunnel middle. The freezing length is closely related to air temperature and train velocity. And also, the lengths are different at vault and rail of tunnel portal, which indicates that the anti-freezing measure should be different at these positions considering the cost. This paper can provide some reference for determining the anti-freezing fortified length of tunnels in cold regions.

2020 ◽  
Vol 79 (5) ◽  
pp. 2201-2212
Author(s):  
Shunhua Zhou ◽  
Zhiyao Tian ◽  
Honggui Di ◽  
Peijun Guo ◽  
Longlong Fu

2014 ◽  
Vol 716-717 ◽  
pp. 342-346
Author(s):  
Xiao Jun Zhou ◽  
Bo Jiang ◽  
Yue Feng Zhou ◽  
Yu Yu

On the basis of different landform and multifarious topography in rugged mountainous area in southwest China, typical tunnel portals for single track tunnels in a new high speed railway line have been presented in the paper. The portal comprises headwall, shed tunnel, bridge abutment and its support. Portal with headwall is suitable for tunnel to resist front earth pressure on high and abrupt slope. Shed tunnel is placed in front of headwall so as to prevent rockfall; its outward part is built into a flared one. Meanwhile, the installation of bridge and its abutment are also included in the portal according to landform in the paper.


2003 ◽  
Vol 87 (7) ◽  
pp. 15-21
Author(s):  
Bert Snijder ◽  
Jan Faber ◽  
Rinus Van Ommeren

2020 ◽  
Vol 10 (4) ◽  
pp. 473-496
Author(s):  
Hongling Guo ◽  
Keping Wu

PurposeThis study aims to investigate how opening high-speed railways affects the cost of debt financing based on China's background.Design/methodology/approachUsing panel data on Chinese listed firms from 2008 to 2017, this study constructs a quasi-natural experiment and adopts a difference-in-difference model with multiple time periods to empirically examine the relation between the high-speed railway openings and debt financing cost.FindingsOur results show that opening high-speed railways reduces the cost of debt financing, and this negative correlation is more significant in non-state firms, firms with weaker internal control, and firms that hire non-Big Four auditors. Besides, we explore the impact mechanisms and find that opening high-speed railways improves analyst attention, institutional investor participation, and information disclosure quality, which in turn lowers the cost of debt financing.Research limitations/implicationsThe results imply that the opening of high-speed railways helps to alleviate the information asymmetry and adverse selection between firms and creditors and ultimately reduces the cost of corporate debt financing.Practical implicationsThis paper can inform firms and stakeholders about the impact of opening high-speed railways on debt financing cost: it improves the information environment, reduces the geographical location restrictions of debt financing, ensures the reasonable pricing of corporate debt, and thus promotes the healthy and sound development of the debt market.Originality/valueThis paper provides theoretical support and empirical evidence for the impact of infrastructure construction on the information environment of the debt market in China, which enriches the research on the “high-speed railway economy.” In addition, as an exogenous event, the opening of high-speed railways instantly shortens the time distance between firms and external stakeholders, which gives us a natural environment to conduct empirical research, thus providing a new perspective for financial research on firms' geographical location.


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