Detailed Explanation of the Application of Oxygen Sensors in Tunnels
Que'er Mountain is a must-pass point on National Highway 317, the vital transportation route from Sichuan to Xizang. The Que'er Mountain Tunnel Project is located between Garze Prefecture and Dege Gangtuo, serving as a key project for crossing Que'er Mountain. It is also the world’s first extra-long highway tunnel built at an altitude of over 4,300 meters. The project consists of two main parts: the main tunnel and the approach roads. The tunnel is 7 kilometers long with two lanes in both directions, with a total investment of 1.15 billion yuan, and is designed to accommodate a daily traffic volume of 5,000 vehicles.
For a long time, Que'er Mountain has been a bottleneck on this vital route. Under normal driving speeds, crossing the mountain takes more than one hour. In winter, after road icing, the travel time can extend to nearly three hours. Once traffic control is implemented, this lifeline is completely cut off.
On November 10, this situation was changed. After more than 10 years of scientific research and 5 years of arduous construction, the 7,079‑meter Que'er Mountain Tunnel was fully completed. If construction proceeds smoothly, it will open to traffic by the end of 2017, eliminating the long-standing traffic bottleneck and opening an economic artery for poverty-stricken counties such as Dege.
The significance of the Que'er Mountain Tunnel is self-evident. However, at such a high altitude with an average annual temperature of minus 18 degrees Celsius, ensuring smooth construction first requires solving the oxygen supply problem. When oxygen is scarce, not only do workers become inefficient, but even machinery may fail to operate normally.
“The oxygen content inside the tunnel is estimated to be only about half of that in the Chengdu Plain,” said a person in charge from the Southwest Research Institute, who participated in the tunnel’s research and development. As early as 2004, the institute launched a major research project: Research on Construction Technology of Extra-Long Tunnels Under High-Altitude, Low-Temperature, Low-Pressure and Low-Oxygen Conditions.
How was the problem of oxygen deficiency solved? To address this, the construction company built a dedicated oxygen station outside the tunnel portal, which continuously supplies oxygen into the tunnel through large-diameter pipelines. Even so, actual operation is far more complicated.
In August of that year, members of the research team went to Que'er Mountain again for investigation and exploration. The experience left a deep impression on Zhang Bo, a technical engineer from the Southwest Research Institute. He recalled that the roads on Que'er Mountain are winding and tortuous, requiring extreme caution while driving. Although the scenery outside is magnificent, as altitude gradually rises, the excitement of enjoying the landscape is replaced by discomfort such as breathing difficulties and chest tightness.
“We felt this way just being on the mountain; the conditions inside the tunnel are even worse,” Zhang said. Although the basic oxygen supply in the tunnel was resolved, newly arrived workers still need to adapt to high-altitude construction and often go to the infirmary outside the tunnel portal for oxygen inhalation every few hours. In fact, to speed up construction, some workers carry oxygen cylinders directly into the tunnel: “Work for a while inside, then come out to breathe oxygen for a while. The hardship of such a scene is hard to imagine for those who have not experienced it.”
Due to the high altitude and enclosed tunnel environment, low oxygen concentration causes chest tightness and dyspnea. Meanwhile, the oxygen station continuously feeding oxygen into the tunnel may lead to excessively high oxygen concentration, which can cause oxygen poisoning. Therefore, real-time monitoring of oxygen concentration is essential.
