? The total length of Qinghai-Tibet Railway is 1 142km, which is completed in three sections. In 2002, the Wang Kun (Kunlun Pass)-Tangwang (Tanggula Pass) section of the Qinghai-Tibet Railway was completed, with the most complicated geology and the biggest technical problem, with a total length of 4 10 km. There are ten key projects in this section, namely the Sixth Bridge (Sanchahe Bridge, Xueshuihe Yangtze River Source Bridge, qingshui river bridge, Frozen Spring Bridge, Chumar River Bridge and Balacaiqu Bridge); Two tunnels (Fenghuoshan Tunnel and Kunlun Mountain Tunnel); Two roads (Wang Kun-frozen spring frozen soil subgrade; Frozen spring-permafrost subgrade of Chumar River). Three technical problems in these ten projects are also the most concentrated and prominent. Researchers and technicians have effectively solved three technical problems through field research on Kunlun Mountain Tunnel and Fenghuoshan Tunnel:
First, the frozen soil problem
When roads are built on frozen soil, the subgrade will be unstable with the change of temperature. Because the temperature in the Qinghai-Tibet Plateau varies greatly every year, the highest temperature is 38℃ in summer and the lowest temperature is -40℃ in winter. In high temperature season, frozen soil melts, forming hot melt lakes and underground rivers, and the roadbed boils and slides, forming washboard roads; When the temperature drops, the subgrade freezes or even expands abnormally, forming a frost heaving ball. There are soil-bearing ice, saturated frozen soil, fissure ice, sandstone, mudstone and sediment interbedded in frozen soil. The rise of temperature will cause hot melt expansion, especially when the open-cut tunnel is excavated, the slope will be unstable, slump and the base will be muddy. After tunnel excavation, the arch will fall off seriously and even collapse. After the operation of the tunnel, the structure will be damaged due to repeated freezing and thawing, which will affect the operation safety. After the railway is opened to traffic, a lot of waste heat will be discharged from the car, which will have an impact on the railway subgrade. In order to solve the frozen soil problem, experts adopted the following methods to ensure the stability and durability of subgrade:
? 1? Using flaky ventilation subgrade, flaky ventilation berm, laying thermal insulation materials, using hot rod technology. (Ventilation subgrade and ventilation berm make air convection fast, make subgrade temperature consistent with surrounding temperature, and it is not easy to form local hot spots, which is beneficial to subgrade stability).
2? Replace roads with bridges in frozen soil and unstable places (bridges are built on frozen soil, but there is no water below, only unstable frozen soil), such as qingshui river bridge.
3? Waterproof insulation layer is set in tunnel engineering lining.
4? Re-study and formulate technical standards for concrete durability to improve the durability of concrete structures. In order to prevent turtle lines from appearing on the pier due to thermal expansion and contraction, so that the concrete is in close contact with the frozen soil, negative temperature maintenance measures are taken, and measures such as digging wells for refrigeration and outdoor cooling are taken in summer to keep the temperature around 10 degrees. In winter, measures such as baking, adding antifreeze and wrapping quilts on piers are taken to ensure the durability and frost resistance of concrete.
Second, the problem of cold and lack of oxygen.
As mentioned earlier, there are 960 kilometers along the Qinghai-Tibet Railway with an altitude of more than 4,000 meters, accounting for 84% of the total length of the whole line, and the perennial temperature in many places is below-10℃. People often say: "When you arrive at Kunlun Mountain, you are dying; After five beams, I cried and shouted to my mother. On the windy volcano, those three souls are dead. " At an altitude of more than 4000 meters, people often feel dizzy and sick, as if they were stepping on a mass of cotton. People who lack oxygen will have symptoms such as headache, brain swelling, chest tightness and shortness of breath, insomnia at night, and induce diseases such as brain edema and pulmonary edema. The air is thin, cold and lack of nutrition, which is called "the forbidden area of life". Cold and lack of oxygen seriously threaten the builders in the construction of Qinghai-Tibet Railway. Usually, people only pay attention to the cold and lack of oxygen in the train after opening to traffic, and pay less attention to the millions of troops engaged in construction in the open air. However, the problem of cold and lack of oxygen will not pose a great threat to passengers in the car after opening to traffic. People just need to take some technology and equipment on the train like an airplane to solve it. But it is a fatal threat to the builders who have been fighting for many years in the construction of the Qinghai-Tibet Railway. Aiming at the problem of cold and lack of oxygen, the Qinghai-Tibet Railway Construction Command and experts have taken the following measures:
1? Adhere to the people-oriented principle, establish a three-level medical security institution, and conduct regular physical examinations and timely treatment for builders.
2? Step-by-step adaptation will be implemented, so that builders can gradually adapt to the climate and environment at different altitudes from low to high, and the operation time and labor intensity will be limited.
3? Strengthen the construction of medical equipment and medical personnel. At present, there are more than 400 medical personnel on the construction site, equipped with more than 900 medical equipment. Buy 16 hyperbaric oxygen chamber (hyperbaric oxygen chamber
Simulating the atmospheric environment close to sea level by means of pressure and oxygenation has a comprehensive effect on treating various diseases caused by hypoxia and depression.
Third, environmental protection.
Qinghai-Tibet Plateau is an important origin and differentiation center of mountain biological species in China, Southeast Asia and even the whole world. It is listed as the highest priority area for biodiversity protection in the world by the World Wide Fund for Nature. The cold climate, sparse vegetation, shallow soil layer and extremely fragile ecological environment are the biggest characteristics of the ecology of the Qinghai-Tibet Plateau. The Qinghai-Tibet Railway just passes through the hinterland of the Qinghai-Tibet Plateau and the "Sanjiangyuan Nature Reserve" and "Hoh Xil Nature Reserve". Therefore, the environmental problems in buildings are very important technical problems. After careful study and planning, experts have taken the following environmental protection measures:
1? Ideological measures: Vigorously publicize the importance of environmental protection and require contractors to increase investment to protect vegetation, frozen soil, wetlands, water sources and wildlife along the line according to law. Advocate "love the environment, wildlife and every inch of land as much as your own life".
2? Technical measures: Take Caiqi Yang as a symbol, strictly divide the construction scope of ore mining and the driving routes of personnel and vehicles to prevent the vegetation outside the construction scope from being crushed and damaged. Domestic garbage is collected by a special person and buried centrally.
3? Legal measures: environmental supervision system is implemented in the whole line, the general headquarters entrusts a third party to monitor the whole process of environmental protection in the whole line, and the provincial environmental protection bureau signs a target responsibility letter with the construction unit to clarify all aspects of environmental responsibility.
4? Engineering measures: in order to protect frozen soil and plateau vegetation, advanced excavation technology is adopted in the construction area of continuous frozen soil; Measures have been taken to replace roads with bridges, and green passages have been set up to protect wild animals (foraging, migration, etc.). ).
It is worth mentioning that in late June, 2002, in order to let 9,000 Tibetan antelopes in labor pass through Wudaoliang site of Qinghai-Tibet line and go to Zhuonaier Lake area in Hoh Xil, the construction workers of China Railway 12th Bureau and 14th Bureau resolutely suspended the construction of some sections, pulled out colorful flags and evacuated personnel and machinery, thus ensuring the smooth migration of Tibetan antelopes.