1Proverbs Concrete materials are the most common general materials in construction projects in the world. Under special climatic conditions, the material properties of concrete are greatly restricted. In high-altitude cold (cold cold) areas, tunnel concrete freeze-thaw damage is one of the main diseases of cold tunnels.
The traditional treatment measures are mainly to prevent drainage, and the measures to strengthen the insulation on the basis of anti-drainage to prevent and cure the tunnel freezing damage, but in high-altitude and cold regions, the temperature difference between day and night is very large, especially when the low temperature is very low, the drainage system often Freeze to death and lose drainage function, resulting in frostbite disease. Therefore, in this area of ​​construction, it is particularly urgent to prevent tunnel frost heave.
With the development of the technology of preventing frost heaving, most of the domestic tunnels currently use insulation construction, and the insulation materials are mainly polyurethane rigid foam. However, it is not ideal from the actual effect of the project. The reason is that the material is easy to age and deform, especially in the high temperature and cold regions, the severe temperature difference cycle and the freeze-thaw cycle, the material stability is not guaranteed, so that the insulation The performance drops sharply and it is difficult to achieve the desired insulation effect.
2 Project Overview The G045 line Sailimuhu to Guogukou section of the highway reconstruction project (referred to as the Saiguo tunnel) is an important section of the G045 line Xinjiang's Sailimuhu to Horgos highway reconstruction project, with a total length of 56.2 km. The tunnel is in a cold region with high latitude and high altitude. The freezing time is long. It generally thaws from October to April. The maximum seasonal frozen soil depth is 170cm, the maximum seasonal snow thickness is 150cm, and the extreme maximum temperature is 40.2°C. The extreme minimum temperature is -36.6 °C, the annual average temperature is 3.0~4.0 °C, and the coldest month average temperature is -14 °C. The bedrock fissure water is relatively developed, and the water inflow near the fault fracture zone is large, and the water quality is still good. The average wind speed in the area is 1.7~2.7m/s, the spring wind is big, the summer is second, the winter is the smallest, and there are many valley winds.
3 The physical and chemical properties of the foamed glass The objective environmental factors of the project determine that the insulation material should have the characteristics of good aging resistance, good volume stability, low water absorption, low moisture absorption rate, low water vapor transmission rate and high combustion grade.
The aging resistance of organic materials is much weaker than inorganic materials. In the relevant standards of the European Union, the service life of organic insulation materials is only 25 years. For tunnel engineering, this is far from sufficient. In addition, organic materials are mostly flammable and flammable materials, which have a great impact on the safety of the project. Therefore, the comprehensive appraisal, the applicability of organic materials in this project is very low.
Representative inorganic materials include rock wool, foamed concrete and foamed glass. Among these materials, the first two materials have high water absorption, and the moisture absorption rate and water vapor transmission rate of the materials are also large, which is determined by the thermal insulation structure of the material itself, and it is difficult to eradicate. In contrast, glass bubbles do not have the above problems.
Foam glass, also known as porous glass, is made of waste glass as raw material, mixed with foaming agent and modifier, and is made by firing at 900C. The thermal insulation characteristics are determined by the physicochemical properties of inorganic glass and the uniform independent bubbles. The effect of surface tension at high temperature causes the glass to form a vitreous structure of a closed material on the inner surface of the bubble while forming a bubble, and the hole and the hole are closed, thereby producing a series of special physical and chemical properties. Therefore, it has the premise of being used under severe conditions.
3.1 Physical properties of foamed glass The physical properties of the thermal insulation material used in this project can be found in Table 1 of the Highway Traffic Technology Application Technical Edition. Its performance can better meet the needs of tunnel insulation projects in severe cold regions.
Table 1 Physical and chemical properties of foam glass Project index value Bulk density / kg compressive strength / MPa flexural strength / MPa volume water absorption / % moisture permeability / ng thermal conductivity / w - dimensional stability will not shrink, expand or rise Wrinkle thermal expansion coefficient / 1 water vapor adhesion 90% relative humidity, weight does not change, flammability, A1 grade, non-combustible material, 3.2 alkali resistance of foam glass. In the conventional concept, it is considered that the erosion of alkali by glassy materials is difficult to deal with. A question, we designed with reference to American ASTM standards.
In order to effectively verify the effect of the insulation of the glass, the engineering department selected a representative test point for different parts of the tunnel to observe the temperature. The main contents of the observation include: foam glass tunnel insulation structure diagram. After the whole construction period, after the insulation construction, the average temperature inside and outside the insulation layer (select the temperature collection every day for a fixed period of time), see Table 3. Table 3 tunnel insulation project temperature average / C Morning noon afternoon, left wall vault, right wall, left wall, vault, right wall, left wall, vault, right wall, inside and outside, inside and outside, inside and outside, inside and outside, inside and outside, inside and outside, the inside and outside of the table reflect that during the entire observation period, the tunnel insulation Destruction within the layer.
The external temperature difference ranged from 12.8 to 18.8 °C, while the internal lining coagulation (2) the temperature difference between the inside and outside of the insulation layer under extreme weather conditions, the average temperature of the soil layer was above °C, effectively preventing the freeze-thaw table. Table 4: Temperature difference between inside and outside in extreme weather / C morning noon afternoon left wall vault right wall left wall vault right wall left wall vault right wall inside and outside inner and outer inner and outer inner and outer inner and outer outer table 4 In extreme weather conditions, the difference between the inside and outside of the insulation layer is in the extreme weather when the average temperature is -33C, the internal temperature does not exceed -. The temperature difference between inside and outside is in the range of 24 ~ 38 ° C, indicating that the insulation layer can be 2C. For lining concrete, it does not occur well at this temperature. At the same time, the data in the table is averaged, and the internal flat frost heave is destroyed.
The mean value is -2C, and the external average value is -33C. This indicates that (3) the extreme temperature and fluctuation range of the inner and outer temperature of the insulation layer, see Table 5. Table 5 Insulation temperature and fluctuation range and fluctuation range / C morning noon afternoon Left wall vault right wall left wall vault right wall left wall vault right wall inside and outside the inner and outer inner and outer inner and outer inner and outer inner and outer of the inner table can be seen from Table 5, the temperature inside the insulation layer extreme range is 11 ~16°C, the average value is 13.5C, the fluctuation range is 5C; the external extreme value of the insulation layer is 27~56°C, the average value is 41.5C, and the fluctuation range is 29°C, indicating that the glass insulation layer can be significant. Reduce the temperature fluctuation of external temperature on the lining concrete, effectively reduce the extreme temperature range, reduce the temperature fluctuation range (and reduce the volume deformation caused by temperature stress).
5 Conclusions (1) The microscopic material structure of foam glass determines its good thermal insulation properties and, more importantly, foaming glass in terms of flame retardancy, durability, water absorption and water vapor permeability (p. 188) For the effective use of archives, enhance the service awareness, participation awareness and benefit awareness of archivists; in the value orientation, from the emphasis on document files to the emphasis on engineering, scientific research and other archives, attach importance to the development and utilization of benefits, and fully tap the huge potential of archives, Maximize the social benefits and economic benefits of archives.
Archives work is a reality-based and future-oriented business. It must have a long-term perspective and link the archival work of the highway sector with the development of modern science and technology and the long-term development of the highway sector. Actively use modern file management methods such as computers and networks to open up new archive management conditions to keep them consistent with the development of the highway industry.
(Continued from page 160) Liao Zhanyu, Li Ying, Yan Echuan, and so on. Deep Foundation Pit Deformation Prediction of Non-equal Interval Time Grey Models. Journal of Hefei University of Technology (Natural Science Edition), 2009, 32 (10) Wu Yiping, Teng Weifu, Li Yawei, et al. Application of Grey-Neural Network Model in Landslide Deformation Prediction. Journal of Rock Mechanics and Engineering, 2007, 26(3): 632-636. Han Wei, Li Ning. A predictive model of formation displacement caused by uneven convergence of tunnel excavation. Yan Liu Dagang, Tao Dejing, Wang next year. Li Cuifeng, Dai Wenzhan, caused by surface subsidence and deformation caused by subway double tunnel construction. Non-equal spacing GM (1,1) model background value construction method and application. Journal of Tsinghua University (Natural Science Edition), 2007, 14 Zhao Caijun, Chen Pengyu, Li Li. Improved GM(1,1) model in the prediction of foundation pit deformation Liu Xiaojun, Wang Xuexiao, Han Hongli. The application of the equal-dimension gray number complementing MGM(1,N) model in the forecast of commodity housing price trends. The performance advantages of Journal of Xi'an University of Architecture and Technology (Natural Science (Continued from page 174) are more prominent, and it is difficult to fully possess other materials.
Foamed glass has the same life characteristics as the structure. Therefore, it has been widely used in construction projects in various fields. It is used in tunnel insulation and objectively obtains a good performance-price ratio.
The actual engineering observation data show that the foam glass insulation system can effectively alleviate the fluctuation of concrete environment caused by external temperature changes, so that it can be in a relatively stable service environment, which plays an important role in protecting the stability of structural materials.
Due to the differences in engineering, the construction methods of the foamed glass insulation structure in different parts of the project are also different, which needs further research and summary.
(Finish)
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