Knowledge of the construction of the Qinghai-Tibet Railway (difficulties and how to overcome them)

I. Why is permafrost the greatest engineering difficulty? Qinghai-Tibet Plateau is the largest piece of permafrost area in China. Permafrost is extremely sensitive to temperature, which has a very big impact on the construction of the railroad. In the frozen state, permafrost is like ice, as the temperature decreases the volume of expansion, built on the roadbed and rails will be it up. In summer, the permafrost melts, shrinking the volume, and the rails are lowered. Repeated freezing and thawing of permafrost alternately, will cause serious deformation of the roadbed, the entire rail appears uneven, and even twisted into a twist, affecting the normal traffic. The 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 been 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 speed of tundra railroads in the United States, Canada and other countries is similarly low. As far as alpine tundra is concerned, the Russian Siberian tundra railroad is longer than ours, at 3,000 to 4,000 kilometers, but its elevation is not high, only 2,000 to 3,000 meters. Although permafrost also exists in Canada, the United States and other countries, they are high-latitude permafrost, which is 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 and frequent tectonic movements, the perennial permafrost here is characterized by high ground temperature, thin thickness and 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. How to solve the problem of permafrost? For the first time, the construction of Qinghai-Tibet Railway adopts the design principle of "active cooling, cooling foundation and protecting permafrost", which is a revolution for "passive heat preservation". In the design, try to bypass the bad permafrost phenomenon development of the section, encountered high temperature is extremely unstable thick 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 roadbed on Qinghai-Tibet Railway, i.e., the bottom of the earth embankment is filled with a certain thickness of schist, and the top is then paved with the earth layer of the roadbed. This 111-kilometer-long "schist layer ventilated roadbed" is the first of its kind in China, which is like a heat dissipation exhaust fan that excludes heat from the embankment and foundation in winter and absorbs less heat in summer, playing a cooling role and effectively protecting the stability of permafrost roadbed. Prof. Zhang Luxin, the head of Qinghai-Tibet Railway construction expert group and permafrost expert, believes that the possibility of large-scale permafrost engineering disease on Qinghai-Tibet Railway is relatively small, and the train speed can reach more than 100 kilometers per hour, so there is no problem to keep smooth flow throughout the year. How to ensure the personal safety of 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 human survival limit of the "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 protection measures, so that the ratio of medical personnel to construction personnel reaches 1.5%-2%, and the whole 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 within half an hour for 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 this technology to promote the whole line *** built 17 large-scale oxygen station, effectively improving the operating environment. Fourth, 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 of the 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 migratory habits of different animals, the passages are designed to be under bridges, above tunnels and on gentle slopes. V. How to protect the plateau vegetation? Builders use segmented construction, vegetation transplantation method, the first construction area of the turf cut into blocks, and then with a forklift will be 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 TuoTuo river, Ando, DangXiong and other high altitude sections, planting and transplanting turf test, after success in the whole line to promote, created the world's plateau, alpine area artificial planting grass test success precedent. In order to protect the plateau wetlands, the Qinghai-Tibet Railway try to avoid wetlands, must pass through the wetlands, generally take the "bridge instead of road", more culverts, roadbed substrate filled with schist and other measures to avoid the road base runoff is cut to prevent the wetlands from shrinking.