The Qinghai-Tibet Railway is the world's highest (the highest point of the line is 5,072 meters above sea level, and the section of the line above 4,000 meters above sea level is 960 kilometers long), the longest line through the permafrost (546.4 kilometers), and the most difficult natural conditions of the plateau railroad.
The three major worldwide problems of permafrost, high cold and lack of oxygen, and ecological fragility have brought great difficulties to the construction of the Qinghai-Tibet Railway.
The Qinghai-Tibet Railway is rich in rare species along the line, the ecological type is unique, primitive, environmentally sensitive, once the damage is difficult to recover.
Why is permafrost the greatest engineering challenge?
The Tibetan Plateau is China's largest permafrost area. Permafrost is extremely sensitive to temperature, the construction of railroads have a very big impact. In the frozen state, permafrost is like ice, as the temperature decreases the volume of expansion, built on top of the roadbed and rails will be it up. In summer, the permafrost melts, shrinking the volume, and the rails are lowered. Repeated freezing of permafrost, melting alternately, will cause serious deformation of the roadbed, the entire rail appears uneven, and even twisted into a twist, affecting the normal traffic.
Construction of railroads in permafrost areas is a worldwide engineering problem that has not been well solved. The world in the permafrost area to build railroads have more than a hundred years of history, but has been built in the permafrost area of the railroad disease rate is very high, the train speed of only 60 or 70 kilometers per hour. Has been a hundred years of history of Russia's first Siberian Railway, there has been a wide range of melting subsidence and frostbite bulge and other diseases, the 1996 survey of the line disease rate of 45%. The second Siberian Railway built in the 1970s, the line disease rate of the 1994 survey also reached 27.5%. The United States, Canada and other countries tundra railroad speed is similarly low.
As far as alpine tundra is concerned, Russia's Siberian tundra railroad is longer than ours, at 3,000 to 4,000 kilometers, but its elevation is not very high, only 2,000 to 3,000 meters. Although permafrost also exists in Canada, the United States and other countries, but they are high-latitude permafrost, more stable. The Qinghai-Tibet Plateau is the world's highest altitude and largest perennial permafrost distribution area in the middle and low latitudes, coupled with the young Qinghai-Tibet Plateau, frequent tectonic movements, the perennial permafrost here is characterized by high ground temperature, thin thickness, extreme instability, etc., and its complexity and uniqueness are unparalleled in the world. The Qinghai-Tibet Railway crosses the area where permafrost is most developed.
Two, how to crack the permafrost problem?
Qinghai-Tibet Railway construction for the first time to take "active cooling, cooling foundation, protection of permafrost" design principles, which is "passive insulation" is a revolution. In the design, try to avoid the bad permafrost phenomenon development of the section, encounter high temperature is extremely unstable thick layer underground frozen land section, take "to bridge through" approach. In the construction, it adopts a number of measures to improve the stability of permafrost roadbed such as schist ventilated roadbed, schist ventilated guard road, ventilated pipe roadbed, hot bar, and laying heat preservation board, etc., and many of these permafrost engineering measures are the first of their kind at home and abroad. There is a special kind of roadbed on Qinghai-Tibet Railway, i.e., the bottom of the earth embankment is filled with certain thickness of schist, and the top is then paved with the earth layer of the roadbed. This 111-kilometer-long "schist layer ventilation roadbed" for the first time at home, it is like a cooling fan, winter from the embankment and foundation to exclude heat, less heat absorption in summer, play a cooling effect, can effectively protect the stability of permafrost roadbed.
Professor Zhang Luxin, head of the Qinghai-Tibet Railway construction expert group and an expert on permafrost, believes that the possibility of large-scale permafrost engineering diseases on the Qinghai-Tibet Railway is relatively small, and that train speeds can reach more than 100 kilometers per hour, so there is no problem in keeping the road open all year round.
Three, how to ensure the personal safety of the builders?
The average annual temperature along the Qinghai-Tibet Railway is below zero degree Celsius, and the oxygen content of the air in most areas is only about half of that in the mainland. Cold and lack of oxygen, wind and sand, strong ultraviolet rays, natural sources of disease, known as the limit of human survival "forbidden zone". How to ensure the safety of builders in the harsh environment is also a worldwide problem.
The Ministry of Railways and the Ministry of Health have formulated perfect health safeguard measures, so that the ratio of medical personnel to construction personnel has reached 1.5%-2%, and the entire line is equipped with more than 3,900 sets (pieces) of conventional medical equipment, so that workers who fall ill are sent to the construction site hospitals in half an hour to receive effective treatment. Following the physiological laws of plateau, all construction personnel in the lower altitude areas "habit service" for a week before being allowed to work at the site. Limit the operating time of personnel, the use of mechanical construction, reduce labor intensity. In order to prevent plateau oxygen deficiency, the construction unit at an altitude of 4,500 meters to 5,100 meters at the creative use of hyperbaric oxygen chamber, filling the gaps in medicine at home and abroad. It is the first time in the world to conduct scientific research on artificial oxygen production at high altitude. At an altitude of 4905 meters in the wind volcano tunnel, developed an hourly production of 24 cubic meters of high-purity oxygen plateau medical oxygen equipment, and will be summarized in the promotion of this technology, the whole line *** built 17 large-scale oxygen station, effectively improving the operating environment. The scientific and technological achievements of "the development and application of the wind volcano tunnel oxygen production and supply system of the wind volcano tunnel of the Qinghai-Tibet Railway" in the construction of the Wind Volcano Tunnel have filled the blank of the high-altitude oxygen production technology in the world at present.
Four, how to protect wildlife?
In order to protect the Tibetan Plateau unique and extremely valuable wildlife resources, the railroad line as far as possible to avoid wildlife habitat, activities in key areas, the Tibetan section of the project bypassed the Linzhou Pengbo Black-necked Crane Reserve. For the road sections that must pass through wildlife activity areas, experts are organized to study wildlife protection issues, grasp the distribution habits and migration patterns of wildlife along the line, and minimize interference with them. Along the Qinghai-Tibet Railway, 33 wildlife corridors have been set up, with a cumulative width of nearly 60 kilometers along the route. According to the migration habits of different animals, the channel is designed for the bridge below, above the tunnel and gently sloping level crossing three forms.
V. How to protect plateau vegetation?
Builders use segmented construction, vegetation transplantation method, the first construction area of the turf cut into blocks, and then forklift the turf along with the soil to the turf transplantation area, a person responsible for maintenance. After the roadbed is formed, then the turf transplantation is restored to the roadbed slope. To the south of the Kunlun Mountains, the natural conditions of the better sections, selected grass species suitable for plateau growth, supplemented by suitable spraying, mulching and other technologies, try to restore the surface vegetation. In Tuotuohe, Ando, Dangxiong and other high-altitude sections, planting and transplantation of turf test, after the success of the whole line to promote, creating the world's plateau, alpine areas of artificial planting of grass test success precedent.
In order to protect the plateau wetlands, the Qinghai-Tibet Railway tries to avoid the wetlands, must pass through the wetlands, generally take the "bridge instead of the road", more culverts, the roadbed substrate filled with schist, and other measures, to avoid the road base under the runoff is cut to prevent the wetlands from shrinking.