The World's First High-Altitude Tunnel Rail Grinding Construction Successfully Completed!


Recently,Independently produced by Baoji CRRC,the GMC-48JS dual-powered rail track grinding train has successfully completed the 66.7 km (467 times/km) rail grinding task of  Guanjiao Tunnel of Qinghai-Tibet Railway at high altitude,which is known as "the longest tunnel in China".The high-altitude tunnel grinding  not only meets the designed profile grinding requirements,  but completely achieves excellency in the GQI evaluation,  adding a beautiful touch to the quality improvement and reconstruction project of Xige 2nd Line.(meaning "a ladder to the sky" in Tibetan) is the only way to Lhasa from inland areas. The weather is harsh there due to extreme coldness and thin air, and the winter is quite long with snow the whole year.  

The Xinguanjiao Tunnel is designed as two parallel single-track tunnels, with a length of 32.645 kilometers and a designed speed of 160 kilometers per hour. It is one of the world's high-altitude and extra-long tunnels, and also "the longest tunnel in China", with a parallel tunnel distance of 40 meters, and the elevation rising from 3,400 meters to 3,800 meters.

After being put into operation in 2014, most rails of Guanjiao Tunnel have had defects of fish scale scratches, fat edge, etc. after long-time wheel rolling. Rail grinding is an effective way to eliminate rail defects, improve the wheel-rail interaction and prolong the service life of rails. However, there have been many problems in the operation process of the traditional internal combustion grinding train, including exhaust gas pollution, noise pollution, the speed limit for long ramp operation, overall overheating of the engine and hydraulic systems for long tunnel operation, reduced engine power as the altitude increases, etc. Therefore, the grinding of rails at high altitudes, long ramps, and long tunnels has always been a major problem in China.

To eliminate the rail defects of Guanjiao Tunnel, Baoji CRRC quickly organized a 20-people team to support Guanjiao Tunnel after receiving the task, and carried out grinding construction with its self-developed GMC-48JS dual-power rail track grinding train.  

Adopting dual source power AC electric drive technology designed for large road maintenance machinery, the train is equipped with two power sources: diesel generator sets and overhead contact network, which can be seamlessly converted.  

Independently developed by Baoji CRRC with completely independent intellectual property rights, the train can effectively eliminate or solve the problems of exhaust and noise pollution of the traditional internal combustion-powered rail grinding train, over-temperature and even shutdown of the engine and hydraulic system of the long tunnel operation, the speed limit of the long ramp operation and power reduction as altitude increases, as well as improve operational efficiency, reduce operating costs and cut carbon emissions, satisfying the national policy requirements of energy saving, environmental protection and high efficiency.  

The grinding team of Guanjiao Tunnel started on-site construction on July 13, and successfully completed construction on July 26. During the 14 days' work, everyone was united as one and made joint efforts to such difficulties as short preparation time, long average daily operation time, and harsh working environment in high-altitude tunnels, and ensured the complete success of the grinding construction of Guanjiao Tunnel by providing whole-process instructions, formulating reasonable plans and carrying out careful equipment maintenance. During this period, they:

#completed 14 skylight construction tasks in total

#completed the grinding task of 66.7 kilometers (467times/km) (including 65 kilometers of pure tunnel grinding (455 times/km)

#completed an average of 4.76 km/skylight (33.3 times/km/skylight) (including 8 times of upward grinding and 6 times of downward grinding) with an average lockdown time of 240 minutes and an average pure operation time of 171 minutes.  

Fig.: After rail grinding

After the grinding work is completed, the surface of the rails took on a new look. The average GQI of the rail profiles was increased from below 60 points before grinding to above 90 points, with an excellent overall evaluation.


Baoji CRRC chose to overcome the difficulties andcontinued to embrace innovation.The GMC-48JS dual-powered rail track grinding train in Qinghai-Tibet Railway  has also opened a new chapter in innovating maintenance modes of long rail tunnels!

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