The breakthrough of three world-class problems, "frozen soil, ecological fragility, cold and hypoxia", directly determines the success or failure of the construction of the Qinghai-Tibet line, and has also become the focus of previous social attention.
The so-called frozen soil, generally speaking, is the general name of soil and rock with ice below zero temperature. According to the duration of the frozen state, things that freeze in winter and completely melt in summer can be called seasonal frozen soil; A frozen state that lasts for two years or more is called permafrost. Frozen soil accounts for about 25% of the total land area of the earth, and China's frozen soil area is about 2 1.5 million square kilometers, accounting for 22% of the land area, ranking third in the world.
The formation, evolution and action mechanism of frozen soil are very complicated, but it is not difficult to understand. Simply put, frozen soil is like a popsicle. Winter will be hard, and summer will become a soft pile. In fact, when frozen, frozen soil is even harder than rock. There are no obstacles to building a house or building a railway on such frozen soil, but the problem is that when the temperature of frozen soil rises in summer or because of various disturbances, it will begin to melt, and the original hard structure will become very fragile, leading to a decline or even disappearance of bearing capacity. At this time, both railways and ordinary houses will be deformed; On the other hand, frozen soil will expand and deform again in winter, which will also cause serious damage to the project. Frost heaving in cold season, melting and sinking in warm season, year after year. This kind of frozen soil is permafrost, or unstable frozen soil, and the first problem to be solved by Qinghai-Tibet Railway is it.
The No.1 Railway Survey and Design Institute of China Railway Construction Co., Ltd. provided a scientific basis for solving the "three major problems" in survey and design, and effectively promoted the solution of the "three major problems". In particular, the solution to the problem of "frozen soil".
Generally speaking, frozen soil is a geological problem, which can also be said to be a problem involving environmental geology. However, it is not comprehensive to know and understand the frozen soil problem only from the perspective of geological work. From the point of view of ecosystem, the frozen soil of Qinghai-Tibet Plateau is a very important part of the unique biosphere of the plateau. Successfully solving the frozen soil problem is not only the internal need to ensure the quality of Qinghai-Tibet railway construction, but also the internal need to protect the unique ecological environment of the plateau. Therefore, solving the problem of frozen soil construction itself is also an important task to solve the environmental protection of Qinghai-Tibet Railway.
First, solve the frozen soil problem.
Frozen soil is the biggest problem in the construction of Qinghai-Tibet Railway. The disease rate of frozen soil engineering in the world is generally around 30%. Most of the 550km permafrost regions that the Qinghai-Tibet Railway passes through are high-temperature permafrost regions, which are high-risk areas for engineering diseases. In addition to the common problems of thaw settlement and frost heaving, there are various phenomena of bad frozen soil, which will have a serious impact on the stability of the project if it is not handled properly in design and construction.
How to actively protect frozen soil and reduce the impact of engineering on frozen soil is the main starting point for forming technical route in survey and design. Based on this, the Railway No.1 Survey and Design Institute has formed a scientific and advanced technical route with the concept of ecological environment protection, that is, under the guidance of the fundamental technical route of "cooling foundation", it has realized three major changes in design ideas, namely, "from static design concept to dynamic design concept, from passive thermal insulation measures to active cooling measures, and from single engineering measures to comprehensive treatment measures". A comprehensive solution with active protective measures as the main and passive protective measures as the auxiliary is formulated, and comprehensive engineering measures with active cooling such as flaky subgrade, hot rod and gravel slope protection as the main and passive protective measures such as laying thermal insulation materials as the auxiliary are widely adopted. Among them, rubble subgrade combined with gravel slope protection measures, rubble berm combined with gravel slope protection measures are the most widely used in Qinghai-Tibet Railway, and have good effects on frozen soil environment protection. The survey, design, scientific research and practical effects of frozen soil engineering are as follows:
First, technical standards such as "Interim Provisions on Engineering Survey, Design, Construction and Acceptance of Qinghai-Tibet Railway Plateau Permafrost Area" have been formulated, providing a basis for the construction of Qinghai-Tibet Railway.
Second, the detailed geological survey and the survey of unfavorable geological phenomena have been completed, and the distribution and development characteristics of unfavorable frozen soil phenomena of thawing and frost heaving in permafrost regions across the line have been basically found out, which provides a scientific basis for taking engineering measures according to local conditions.
Thirdly, the frozen soil experimental engineering research has achieved many phased results. There are 38 scientific research projects, and more than 20 units including scientific research, universities and construction participate in scientific research together. At the initial stage of Qinghai-Tibet Railway construction, five test sections were selected according to different geothermal zoning, different ice content, different geological conditions and hydrological conditions, and large-scale field tests and scientific research were carried out, involving subgrade, bridge, tunnel and environmental protection. Through field test and scientific research, the design and construction work are dynamically guided. At present, the adaptability and rationality of passive protective measures such as flaky ventilation subgrade, flaky and gravel slope protection, hot rod cooling foundation and laying thermal insulation materials in design have been confirmed.
Fourthly, a large number of facts have preliminarily proved the effectiveness of frozen soil engineering measures on the Qinghai-Tibet line. The engineering construction practice in the past three years shows that the design scheme has an accurate understanding of the distribution scope, characteristics, manifestations and influence on the project of the phenomenon of bad frozen soil along the Qinghai-Tibet Railway. After two freeze-thaw cycles, the civil structure of the whole line is safe, stable and in good condition, which has achieved the expected goal and proved that the engineering measures adopted in the design are effective.
Second, solve the problem of protecting the ecological environment.
Qinghai-Tibet Railway is a railway construction project with the most environmental problems, the highest environmental sensitivity and the highest degree of concern. According to the principle of "prevention first, protection first" established by the State Environmental Protection Administration and other ministries and commissions, and on the basis of a lot of preliminary work, Railway No.1 Survey and Design Institute concentrated the advantages of domestic first-class scientific research teams such as Academy of Sciences, compiled documents such as environmental assessment and water and soil conservation plan, and compared and optimized the design plan with a brand-new environmental protection concept. In view of the fragile ecological environment, a series of studies have been carried out on wildlife passage, vegetation restoration and reconstruction, wetland frozen soil protection and so on. , and achieved phased results. Seven main measures were taken in the design and construction:
1. Optimize the line scheme. In order to protect the nature reserve, the route chooses a bypass scheme; In order to avoid soil erosion caused by a large number of excavation, a new scheme of replacing subgrade with Shunhe Bridge is adopted in the design. Bridges are used to replace roads in the design of wetland sections crossing wetlands and frozen soil slopes.
2. Vegetation and landscape protection plan. Cancel or relocate the spoil ground that does not meet the requirements of landscape and vegetation protection, or conflicts with local regional development planning and grassland protection. All kinds of construction sites, construction roads and construction camps have also been planned in a unified way, and the scope and quantity of land use have been defined, so as to minimize the construction scope and reduce the impact on the ecological environment in other areas.
3, topsoil preservation and turf transplantation scheme. With the unified deployment of the construction unit, the topsoil and vegetation of subgrade basement, borrow yard, construction access road and other projects have been transplanted and preserved by the construction unit in different places.
4. Design wildlife migration channels. There are 33 wildlife passages in Qinghai-Tibet Railway Project, which are located under the bridge, above the tunnel and on the gentle slope. Practice has proved that the effect is obvious.
5. Restoration and reconstruction of alpine vegetation. The experiment of vegetation restoration was successfully carried out, and the transplantation and utilization of in-situ surface turf uprooted during construction were studied and designed. Turf uprooted from embankment foundation and borrow yard shall be maintained in proper places, and transplanted to embankment slope or borrow yard after construction is completed, so as to protect and restore natural vegetation to the maximum extent.
6. Establish an environmental protection management system and strengthen the supervision of environmental protection. The construction of a "four-in-one" environmental protection management system is organized by the construction unit, implemented and undertaken by the construction unit, supervised by the engineering supervision unit in the daily environmental protection work during the construction process, and comprehensively monitored by the environmental protection supervision department. Implement the environmental protection target responsibility system, and implement the environmental protection responsibility to the project department, construction team and even individuals.
In the history of railway construction, environmental supervision was introduced for the first time, and a set of relatively perfect environmental management systems such as environmental supervision and inspection, work records, measures review, project inspection and optimization, rewards and punishments were implemented, and the environmental protection one-vote veto system was implemented for high-quality model projects.
7. The design of Qinghai-Tibet Railway Station reflects the integration of architecture and plateau landscape. In the design of Qinghai-Tibet railway station building, we should adhere to the four principles of humanization, characteristics, culture and landscape, make at least three different design schemes for each station building, and optimize and compare the design of different types of 17 stations along the whole line, so that the station building design can reflect the humanistic characteristics of harmonious echo of architecture, landscape and Tibetan culture on the basis of considering practicality. At the same time, the design also takes into account the extensive use of clean energy such as solar energy.
These measures have proved to be very effective and have been widely praised. From August 9 to 14, 2003, the State Environmental Protection Administration, together with the Office of the National Leading Group for Qinghai-Tibet Railway Construction, the Ministry of Railways, the Ministry of Communications, the Ministry of Water Resources, the Ministry of Land and Resources, and the State Forestry Administration, invited the relevant departments of Qinghai-Tibet and some experts in ecology, flora and fauna to form an inspection team. Through the investigation of the environmental protection work during the construction of Qinghai-Tibet Railway, it was concluded that the environmental protection work during the construction of Qinghai-Tibet Railway was at the leading level in key domestic construction projects and had a demonstration role
Third, solve the problems of cold and lack of oxygen.
The average altitude of the Golmud-Lhasa section of the Qinghai-Tibet Railway is 4440 meters, and the oxygen content is only about 50% of the sea level, so the natural conditions are very bad. According to the characteristics of the plateau, adhere to the "people-oriented" design concept, use a large number of mechanized operations in survey, construction and operation, establish and improve a three-level medical security system covering the whole line, and establish a living supply base to overcome and alleviate the altitude sickness of field personnel and ensure their life safety. The main measures are as follows:
1. The line standard is improved in the design. The purpose is to ensure that the train passes through the plateau safely and quickly, and to minimize the impact of altitude hypoxia on passengers. Appropriately raise the design standard and increase the curve radius at an appropriate speed. The minimum curve radius 1200m is 850km long, which is more than 70% of the total length of the line. The design speed of the whole line exceeds 100km, and the top speed can reach 140km.
2. Safeguard measures in the construction stage. The choice of construction machinery and equipment is "choose large equipment and use less small equipment;" Advanced tunneling, drilling, excavation and handling machinery are selected and equipped with pressurization equipment. "
(1) Choose construction machinery with strong adaptability and high power on the plateau, so as to reduce the labor intensity of construction personnel as much as possible and improve work efficiency.
(2) During the tunnel construction, measures such as diffuse oxygen supply should be taken to strengthen the ventilation in the tunnel, so as to ensure the normal and safe work of the construction personnel under the conditions of lack of oxygen on the plateau and poor living conditions.
(3) The building structure adopts light modular design, which reduces the labor intensity of construction personnel and speeds up the construction progress.
2. Safeguard measures in the operation stage.
(1) On the premise of meeting the transportation capacity, it is considered to distribute stations from near to far, with as few stations as possible, reducing on-site facilities and personnel, and saving engineering investment and maintenance costs.
(2) The traction power of the train adopts advanced high-power diesel locomotive, and the locomotive routing adopts 1 140Km long route, which reduces the distribution of crew and locomotives along the line, and accordingly reduces the operating cost.
(3) Applying advanced information technology at home and abroad as a world-class plateau railway demonstration project, laying 60-core communication trunk optical cable, erecting 35KV power through line, adopting internationally advanced GSM-R system as the technical standard of wireless digital mobile communication of Qinghai-Tibet Railway, and combining with GPS satellite positioning technology, forming an information engineering basic platform, forming a remote dispatching command and connecting train control (signal) RBS system, thus reducing the station ground signal facilities. With the wide application of information technology, all 34 stations in the whole line are unattended except the business operation station.
(4) Establish a new maintenance and management mechanism. Make full use of the existing professional road sections in Golmud, and do not add new road sections such as vehicle services, public works, electricity services, water and electricity, and housing construction. Large road maintenance machinery is used for line maintenance and overhaul. Due to the adoption of high-standard reliable facilities and maintenance-free and less-maintained equipment, the maintenance of other facilities or equipment is outsourced to reduce the number of employees.
(5) Adopting new plateau buses to provide passengers with a more comfortable riding environment.