Located on the Qinghai-Tibet Plateau at an altitude of 4,750 meters above sea level, the Wind Volcano Positioning Observatory of the Northwest Courtyard of China Railway. (Data map) Courtesy of China Railway Northwest Research Institute
Lanzhou, China, December 24 (Pan Bo) One of the "heroes" behind the glorious history of China's plateau railway construction, the China Railway Northwest Scientific Research Institute (hereinafter referred to as "China Railway Northwest Academy"), is committed to the scientific research and innovation of the special subgrade foundation of China's plateau railway, and has worked hard for 60 years to solve the "frozen soil problem" of the Qinghai-Tibet Railway.
2021 happens to be the 20th anniversary of the construction of the Qinghai-Tibet Railway, the world's longest and highest plateau railway known as the "Road to Heaven" and "Oriental Hada", the 15th anniversary of its opening and safe operation, and the 60th anniversary of the establishment of the Northwest Science Research Institute of China Railway.
The picture shows the Wind Volcano Observatory Science City in the 1970s. (Data map) Courtesy of China Railway Northwest Research Institute
Frozen soil occurs because the soil contains more or less water, and when the temperature drops to zero degrees or less, the water in the soil will condense into ice and freeze the soil. Frozen soil is very sensitive to temperature changes and will "gain weight" and "thinner" as the temperature rises and falls.
Just like the "soft pear" that Lanzhou people love to eat, when the pear is frozen hard, the water in the causal meat freezes and expands, and the teeth are "nowhere to go". However, as the temperature rises, the frozen pear becomes soft and collapsed after melting, and you can taste the sweet pear juice by simply sucking it gently.
Why did permafrost become an obstacle to the construction of the Qinghai-Tibet Railway?
Science and technology workers of The Northwest Institute of China Railway collect instrument data at the Wind Volcano Observatory. (Data map) Courtesy of China Railway Northwest Research Institute
Because the train needs to cross more than 5,000 meters of high mountains, span more than ten kilometers of valleys, and most importantly, there are hundreds of kilometers of permafrost to block there. It is not easy to overcome these difficulties in the plains, not to mention the thin air on the Qinghai-Tibet Plateau, how can people lay rails and build bridges when they need oxygen cylinders for a slight movement?
In addition, the volume of ice should shrink when it melts into water, and the volume of water should expand when it freezes into ice. This popular principle of nature causes the formation of frost heave uplift and melting sinking in the frozen soil area in winter and summer, and this unstable geological change directly leads to the difficulty of building roads, railways, bridges and houses in the frozen land area. Overcoming the huge difficulties brought by this frost heave and thaw to the construction of permafrost projects has become the core technical problem of building railways in the frozen soil area of the Qinghai-Tibet Plateau.
The scientific and technological workers of the Northwest Institute of China Railway shoulder to shoulder carry the geological drilling rig. (Data map) Courtesy of China Railway Northwest Research Institute
The Qinghai-Tibet Railway has crossed 545 kilometers of continuous permafrost, which is currently the longest plateau railway in the world that has crossed permafrost. (The average annual geothermal temperature is 160 km below -1.0 °C permafrost area, the average annual ground temperature is 275 km above -1.0 °C permafrost zone, and the melting zone is 110 km.) Therefore, the construction of the Qinghai-Tibet Railway faces the problem of more widely distributed high temperature and high ice content permafrost, and must fully consider the adverse effects of rising global temperatures, human activities during operation, and geological diseases caused by environmental changes. Therefore, the problem of frozen soil is the biggest difficulty facing the construction of the Qinghai-Tibet Railway, and it is also the most critical issue to ensure the stable quality and safe operation of the Qinghai-Tibet Railway Project.
The picture shows the Qingshui river pile foundation test site in the northwest courtyard of China Railway. (Data map) Courtesy of China Railway Northwest Research Institute
In the process of challenging the "impossible", the Northwest Institute of China Railway has completed two tasks: first, for the purpose of scientific research, it has built the only wind-volcano permafrost observation station on the Qinghai-Tibet Plateau (4750 meters above sea level) that is manned all year round, accumulating scientific research big data; second, with the purpose of overcoming the road construction problem, it has built the first (483 meters long) frozen soil test subgrade and carried out a series of engineering experiments.
Wind Volcano (also known as Mount Longqing Gibb), because of its reddish-brown color, is very eye-catching, as if it has been burned by fire countless times, so it is named. The climate environment in the wind volcano area is extremely harsh, the average annual temperature is -5 ~ 7 °C, the minimum temperature is -41 °C, and the oxygen content in the air is only about 50% of the plain area, which is known as the "forbidden area of life".
The picture shows the application of hot rod technology in the frozen soil area of Qinghai-Tibet Railway. (Data map) Courtesy of China Railway Northwest Research Institute
The wind volcano area concentrates on the three world-class scientific and technological problems of building the Qinghai-Tibet Railway "alpine and hypoxia, ecological fragility, and permafrost", and has also been asserted by foreign experts who came to investigate, "The Qinghai-Tibet Railway cannot pass through the wind volcano".
However, as early as 1961, the scientific and technological personnel of the Northwest Institute of China Railway established China's first plateau permafrost positioning observation station with the highest altitude, the largest number of observation projects, and the annual duty in the hinterland of the qinghai-Tibet Plateau permafrost, and was also the earliest scientific research institution in China to conduct frozen soil observation and research, and successively carried out research on 36 scientific research topics in 9 professional fields such as regional permafrost, frozen soil mechanics, thermal, subgrade, bridge and culvert, housing construction, water supply and drainage, building materials, ecological environmental protection, etc., and achieved 29 major scientific research results. 15 million sets of data were continuously measured, laying a solid foundation for cracking the worldwide problem of permafrost and providing technical support for the decision to build the Qinghai-Tibet Railway.
The picture shows that after the opening of the Qinghai-Tibet Railway, the train passes through the Wind Volcano Observation Station of the Northwest Courtyard of China Railway. (Data map) Courtesy of China Railway Northwest Research Institute
In 1976, researchers from the Northwest Institute of China Railway built the first (483-meter-long) test subgrade on the Qinghai-Tibet Plateau Wind Volcano, known as the roof of the world, known as the "railway without steel rails". The researchers used different subgrade cross-sectional forms and protective measures to divide the test subgrade into 23 test sections. Including embankments, grabens, L-shaped flexible retaining walls, test culverts.
At the same time, the researchers took a variety of forms of protection, laying turf, clay, asphalt expanded perlite, phenolic resin board, aerated concrete, foam plastic, cement perlite slab a total of seven kinds of insulation materials on the slope or substrate, using different slope rates and anti-drainage measures for observation and testing. In addition, the design principles, cross-sectional forms and protective measures of the subgrade project of the thick underground ice section, the anti-drainage measures of the insulation of the subgrade engineering are proposed, and the artificial upper limit and frost heave change law of the frozen soil subgrade are mastered, and the engineering design and construction experience of the subgrade of the thick underground ice section is obtained.
Liu Tieliang, a late permafrost expert of the Northwest Courtyard of China Railway, on the basis of long-term observation and research on the 483-meter test subgrade of the wind volcano, summed up a set of methods for protecting the railway subgrade by laying turf and vegetation in the permafrost area of the plateau, and the data and calculation methods used can accurately calculate the optimal thickness of the insulation layer of the slope of the road graben in the frozen land area of the Qinghai-Tibet Plateau, and pioneeringly solve the problem of subgrade protection of the Qinghai-Tibet Railway. This theoretical achievement of his has been called the "Iron Liang Formula" by the domestic plateau permafrost academic community.
The picture shows the successful passage of the Qinghai-Tibet Railway through the permafrost area. (Data map) Courtesy of China Railway Northwest Research Institute
"Practice is the only test of truth." From the Northwest Institute of China Railway to challenge the "impossible" task of frozen soil, looking back at the process of permafrost research on this section of the Qinghai-Tibet Railway, it can be said that the wind volcano permafrost research base has an extremely important position, it systematically carries the mechanism research task of the core key technology of road construction in the frozen soil area, pioneeringly solves the problem of frozen soil subgrade, strongly supports the successful passage of the Qinghai-Tibet Railway through the permafrost area, and realizes the "driving speed of the frozen soil area reaches 100 km / h" proposed when the Qinghai-Tibet Railway is designed. Non-permafrost areas reach a high driving speed of 120 km / h".
Nowadays, the wind volcano permafrost scientific research base is still like a lighthouse sticking to the Qinghai-Tibet Plateau, through the planting of Internet of Things components in the roadbed, to achieve real-time, automatic, continuous measurement of frozen soil data, and the monitoring data is sent synchronously to the Golmud frozen soil engineering laboratory, through the frozen soil subgrade early warning monitoring system software analysis data to make judgments or issue early warnings, so as to escort the future safe operation of the Qinghai-Tibet Railway.
The three generations of scientific and technological workers of the Northwest Academy of China Railway have passed on the torch, challenged the world-class "impossible", won the "National Excellent Grassroots Party Organization" of the Central Organization Department, the National May Day Labor Award issued by the All-China Federation of Trade Unions and other honors, leaving behind the wind and volcano spirit of "being proud of suffering, having the courage to innovate, diligently pursuing, and dedicating to science". (End)
Source: China News Network