Since the launch of Spring Festival Transportation on January 13, 2017, China’s railways are expected to deliver 0.356 billion passenger trips during those 40 days, rising 9.7% year-on-year.
In recent years, high-speed rail has seen rapid development in China, claiming the world’s largest railway network under construction, the longest railway lines, the highest travel speed, and the maximum capacity to integrate. Under the joint efforts of the Ministry of Science and Technology and the Ministry of Railways, China’s high-speed rail technology improves consistently. “Higher-speed trial rail” program, a representative of China’s high-speed rail technology innovations, marks the transfer of the country’s industry from low-end to high-end. Meanwhile, China’s high-speed rail receives increasing international recognition.
To closely observe the latest progress of this program and look into its technical problems and safety issues, CNKI International Publishing Center (IPC) held a frontier academic forum on “higher-speed trial rail”. Professor Chen Shanxiong, doctoral supervisor of the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wang Mengshu, Academician of the Chinese Academy of Engineering, and Associate Professor Zhou Suxia from Beijing University of Civil Engineering and Architecture attended the meeting.
1. What is the minimum design speed (kilometer/hour) of high-speed rail? What is the design speed of high-speed rails under operation in China? What is the speed of high-speed rail currently under test?
High-speed rail is considered to have design speed in excess of 250 kilometers per hour (on new lines) and operating speed at least 200 kilometers per hour (existing lines) in the initial stage, Zhou said. Two types of high-speed rails are currently under operation in China, with design speeds of 200-250 and 300-350 kilometers per hour, respectively and corresponding operating speeds of 200 and 300 kilometers per hour. The high-speed rail under bench test can run as fast as 605 kilometers per hour. Recently, its highest operating speed is expected to reach 350-400 kilometers per hour, which will rank the world’s fastest speed. Trial operating speed of high-speed rails in France, Japan, Germany, Spain and South Korean also reaches 350-360 kilometers per hour.
2. Why do we research and develop high-speed trial rail?
Zhou said, apart from meeting the requirement of operation, the study of higher-speed trial rail serves the following three purposes: studying the security system of high-speed rail including safety and stability of train at higher speed; providing testing platform for the study on basic scientific problems; providing a platform for examining the application of new materials and technologies, which is further conducive to the improvement and perfection of technical system of high-speed rail.
3. What technical support is required in developing higher-speed trial rail?
According to Zhou, higher-speed rail in China, which was set up in December 2011, has been developing rapidly and experiencing test under the joint efforts of the Ministry of Science and Technology and the Ministry of Railways. The goal is to operate safely and reliably at a higher speed. Technical supports in terms of aerodynamics, pantograph-catenary relationship, traction and brake are required for technology breakthrough centering on raising critical speed, improving traction ability and lowering resistance as well as all-round innovation in system integration, train head, carriage body and bogie, traction and braking system. Ten key technologies include: high-speed AC drive, high-performance bogie, composite braking system, aerodynamic design for appearance, lightweight technology, train auto-control and fault diagnosis technology, carriage sealing technology, denoising and sewerage technology, strong connection between carriages, high-speed pantograph, and tilting carriage body.
Higher-speed rail imposes stricter requirements on the smoothness and stability of tracks, Chen said. Under such circumstance, small deformation is allowed in underground engineering including roadbed, bridge and tunnel and dynamic response is examined at high frequency band. Solutions are awaited to the following technical problems: the regularity of dynamic response of underground engineering and mechanism of disaster under dynamic loading in higher frequency band; the control of small deformation of underground engineering in construction stage and the realization of slight settlement through structure, construction filling and evaluation of underground engineering; recognition fault diagnosis and early warning of small deformation of underground engineering during the operation. Those technical problems set tests for technical ability and skill level of engineering.
4. How to ensure the security of high-speed rail?
Zhou pointed out that security is the top priority of train at such a high speed. Train control system of different braking is generated to ensure the security of high-speed rail. This system comprises a train-mounted subsystem and a ground subsystem. The two subsystems interact with each other through signals to control the running speed and interval between the train and target and to monitor the environment and detect the state of the train. Besides, high-speed train is subject to routine inspection regularly on each system so that problems can be detected and addressed timely.
5. Can higher-speed rail run on the existing high-speed railway lines?
Chen said that the existing high-speed railway lines established according to certain standards usually have safety reserve and space for speed increase. Under ideal conditions, the speed railway lines can support is higher than the design speed. Therefore, the existing high-speed lines, after higher requirements for smoothness are met, can support higher-speed rail. However, the increasing range of speed should be determined in accordance with the smoothness and stability of tracks. In reality, special sections on each railway line such as soft soil roadbed, expansive soil roadbed and karst tunnel make it difficult to effectively control the sedimentation and deformation of underground engineering. Under the interaction between the train and track, track geometry inevitably changes consistently and tracks will become unsmooth geometrically, affecting the comfort and safety of the train at a high speed. On such sections, the requirement of higher-speed rail cannot be met. Thus, existing high-speed railway lines need to be assessed specifically to determine whether they can support higher-speed rail.
6. What natural conditions are required for the construction of higher-speed railway lines?
Chen said that higher-speed rail has stricter requirements for natural conditions of railway lines. It needs to avoid the sections frequently attacked by natural disasters such as landslide, mudflow, strong wind and thunderstorm. The effect of natural disasters on the running of higher-speed rail can be studied in the areas facing most natural disasters so as to make corresponding response plans, which in combination with disaster monitoring and early warning can help reduce the effect of natural disasters on the running of higher-speed rail to a control range.
Zhou pointed out that high-speed rail imposes higher requirements on the weather. For example, strong airflow can affect the running speed and vehicle structure may be affected by the excitation of ground vibrations under the action of airflow; strong rainfall and heavy snow are also safety hazards, under which the running speed must be lowered or the train need to be stopped to ensure the travelling safety. China’s high-speed rail will be exported to the US, Indonesia, Russia, Brazil, etc., where it will display advanced technologies in extreme-cold weather conditions and in complex geological conditions.
7. What are the technical difficulties higher-speed rail face in the fields of civil engineering, mechanical engineering, materials engineering and communication engineering? Are those difficulties resolved worldwide? What are the world leading technologies China has?
Chen said that in the field of civil engineering, there are four technical difficulties in the construction of higher-speed rail: the mechanism of disasters in roadbed under higher frequency loading and environmental coupling; technology for controlling the settlement of underground engineering, including engineering structure optimization, fill material optimization and filling technology; analysis and assessment of small deformation of underground engineering; early recognition, diagnosis and warning of problems occurring in underground engineering during the operation. Those problems under investigation are the research focus worldwide. China takes a leading position in the world in terms of technologies for the analysis and assessment of small deformation of high-speed railway roadbed, undermining dynamic response characteristics of roadbed and the mechanism of disasters, early recognition of problem during the operation, and indexes and standards for fault diagnosis.
Wang added that China also has the world leading technologies for railway tunnel construction and road network planning.
Zhou said, CRH380 train independently developed by China, which can run at a speed of 380 kilometers per hour, is also a leading technology in the world. The third generation traction technology for track traffic developed by China Railway Rolling Stock Corporation, namely permanent magnet synchronous generator system, which enjoys independent intellectual property rights, serves as a strategic tool of China’s high-speed rail to win the market. Continuous welded rail technology on high-speed railway developed by China Railway Siyuan Survey and Design Group remains at the forefront of such technology in the world.
8. Can the running speed of high-speed rail increase to 350 kilometers per hour?
In Wang’s view, the running speed of high-speed rail cannot be raised to 350 kilometers per hour due to the following five reasons:（1）Lifespan. Excessively high speed lowers the lifespan of the train.（2）Safety. It is safer for the train to leave room for higher speed; meanwhile, inspection and fastening will need to be enhanced.（3）Economy. As speed increases, resistance will become larger and cost rises. （4）Braking. It is easy to increase but hard to reduce speed. A train running at a speed of 350 kilometer per hour should begin to slow down seven kilometers or even more than ten kilometers away; otherwise, the train will have to decelerate before it is able to accelerate.（5）Road network planning. Running speed of 350 kilometers per hour is hard to realize in road network planning. The whole system, including traction system, power supply system, signaling system, braking system and wheel-rail system, needs to be re-designed. For example, when two high-speed rails run at a speed of 300 kilometers per hour in opposite directions, relative speed is equivalent to 600 kilometers per hour; under such circumstance, the carriages feel expanding force, while the rear feels attractive force, threatening the stability on the whole. Therefore, the interval between tracks on existing bridges and tunnels needs to be widened, which is a systematic issue.
Additionally, Zhou proposed three problems to be noted if the speed of 350 kilometers per hour should be realized:（1）High-speed railway lines are fundamental, including high-standard design of transverse and vertical sections, high-speed rail roadbed, transition between road and bridge, high-speed rail bridge, high-speed rail tunnel and high-speed railway traction power supply system;（2）High-speed railway safety management system is the nerve center of high-speed rail, including automatic train control (ATC), European train control system (ETCS), centralised traffic control (CTC), high-speed railway detection and diagnosis system, natural disaster alarm system and regular inspection system;（3）High-speed rail passenger service system includes railway station, ticket order and pre-sale system, passenger instruction system in railway station and passenger information display system.
9. Can high-speed rail produce radiation?
High-speed rail, which is a closed magnetic field, is pulled by electric force, so no radiation is produced, Wang said.
10. Will WIFI be available on high-speed rail?
According to Wang, firstly it is technically unfeasible to install WiFi connections on high-speed rail, because the accuracy of sending and receiving signals cannot be ensured on the train running at a high speed. Secondly, frequency is required in many systems for the operation of high-speed rail, such as automatic control system; if WiFi connections are installed, signals will be interfered, which is not conducive to the travelling safety.
Zhou said that along high-speed railway lines, roads are long with multiple points and dangerous terrain. The train often enters the blind zone where the Internet is unavailable. On a high-speed rail, the Internet is unstable; only with a strong WiFi hotspot, people can access the Internet at the same time. Besides, the cost for maintenance is high, hindering the development of WiFi on high-speed rail. However, through the efforts of related departments, those difficulties have been resolved one by one. At present, WiFi on high-speed rail officially enters a phase of testing. Experts claim it will come true in next three to five years.
11. Compared with higher-speed rail, what are the advantages and disadvantages of magnetic levitated (maglev) train?
According to Zhou, with maglev, the train travels along the tracks using magnets to create lift and propulsion without touching the ground. The first maglev train in China was in operation in Shanghai in January 2003. In October 2015, the first maglev lines made in China succeeded in trial running.
Maglev train moves fast and quietly; it is also environment-friendly, economic and comfortable. Its tracks have lifespan as long as 80 years, in contrast with a lifespan of 60 years of ordinary ones. The lifespans of maglev train and wheel train are 35 and 20-25 years, respectively. The annual maintenance costs of maglev train and wheel train are 1.2% and 4.4% of total investment, respectively. The cost for operation and maintenance of maglev train is about 1/4 that of high-speed wheel train.
Zhou said, however, maglev train has the following drawbacks:（1）Once the power is cut off, serious accident will take place.（2）It cannot afford heavy transportation, with transport capacity no more than 1/2 that of high-speed rail.（3）Both construction cost and energy consumption are high.（4）Safety and reliability of signaling and braking need to be examined throughout long-term operation. Besides, it is not suitable for harsh natural conditions and long-distance travel and braking ability in an emergency is unreliable.（5）Strong magnetic field affects human health, ecological environment and the use of electronic products.
JTP's LIU Kang and JIN Ge contributed to this report.