Permafrost Regions Of Qinghai Research Articles

Temperature Load Mode of Bridge in Permafrost Region of Qinghai–Tibet Railway

The Qinghai–Tibet railway is the plateau permafrost railway with the highest altitude and the longest line in the world. The natural conditions along the line are harsh, with many unfavorable factors such as low temperature, strong ultraviolet radiation, and large changes in daily temperature, resulting in frequent bridge damage. In order to study the bridge temperature field and its effect in the permafrost region of the Qinghai–Tibet railway, a long-term field test was carried out, and a calculation model of sunshine temperature field of concrete two-piece T-beam was established based on the principle of meteorology and heat transfer. On this basis, the beam temperature difference load mode, beam section temperature distribution law, and temperature effect were obtained. As revealed, the daily temperature difference of the Qinghai–Tibet railway bridge is large in winter, which is related to the ground’s effective radiation and surface reflectivity, and the maximum value has exceeded the current codes. The beam section temperature field shows “internal heat and external cold” in the morning and “internal cold and external heat” from noon to evening. Under the action of strong radiation and large temperature difference, bridge displacement occurs frequently, by which it is easy to cause damage to rail fasteners and bridge bearings. Based on the field test and finite element analysis, the bridge temperature difference load mode was proposed, which makes up for the deficiency that the relevant codes do not consider the plateau’s special climatic conditions and can provide a reference for the construction of plateau railways such as the Sichuan–Tibet railway.

Analysing the environmental harms caused by coal mining and its protection measures in permafrost regions of Qinghai–Tibet Plateau

Abstract The coal mining has brought a series of ecological problems and environmental problems in permafrost regions. Taking Muli coal-mining area as an example, this article attempts to analyse the environmental harms caused by coal mining and its protection measures in permafrost regions of Qinghai–Tibet Plateau. This article analyses the influence of open mining on the surrounding permafrost around the open pit by using the numerical simulation. The results show that (1) based on the interrelation between coal mining and permafrost environment, these main environmental harm include the permafrost change and the natural environment change in cold regions; (2) once the surface temperature rises due to open mining, the permafrost will disappear with the increase of exploitation life. If considering the solar radiation, the climate conditions and the geological condition around the pit edge, the maximum thaw depth will be more than 2 m; (3) the protection measures are proposed to avoid the disadvantage impact on the permafrost environment caused by coal mining. It will provide a scientific basis for the resource development and environment protection in cold regions.

Numerical analysis on thermal regime of wide embankment in permafrost regions of Qinghai−Tibet Plateau

This study investigated the temperature field and thawing depth of wide embankment for expressway in permafrost regions based on numerical analysis by using finite element method (FEM). According to specific embankment section of Qinghai−Tibet highway, computational region for numerical analysis was defined. And numerical model was developed through FEM software named as ABAQUS and was verified by field observed data. The effects by width and height of embankment on the thermal regime of computational region were analyzed based on FEM modeling. Numerical analysis showed that embankment construction has serious disturbance on the thermal stability of ground permafrost showing as annual average ground temperature and the maximum thawing depth keeps increasing with service time increasing. And larger embankment width leads to poorer thermal stability and more serious uneven temperature field of embankment. Raising embankment height can improve the thermal stability; however, the improvement is restricted for wide embankment and it cannot change the degradation trend of thermal stability with service life increasing. Thus, to construct expressway with wide embankment in permafrost regions of Qinghai−Tibet Plateau, effective measures need to be considered to improve the thermal stability of underlying permafrost.

Study on the effect of the thermal regime differences in roadbed slopes on their thawing features in permafrost regions of Qinghai–Tibetan plateau

Abstract For the permafrost regions, numerical models are established for analyzing the possible changing tendency of the permafrost thawing features under various surface materials, embankment heights and strikes for a period of 50 years. Surface materials are gravelly and asphalt. Embankment heights range from 0 m to 5.0 m with a step of 0.5 m. For the embankment strike, east to west (EW), southwest to northeast (SW–NE), south to north (SN) and symmetrical route are taken into consideration. The thermal boundary condition is with the assumption that the air temperature will warm up by 1.1 °C during the next 50 years. The calculated results indicate that there is a great difference in thawing features between the asymmetrical and the symmetrical routes. Beneath both the gravelly and the asphalt surfaces, for embankments with south-facing and north-facing slopes, which are defined as the shadowy–sunny slope, calculations show: (1) The maximum thaw depth is closely related to time, the surface materials and the embankment heights. The maximum thaw depths of the low embankments have little to do with the roadbed strike. But the maximum thaw depths of the high embankments are very much influenced by the roadbed strike, and it sharply changes with the variation of the embankment heights and climatic warming. (2)The distance from the location where the maximum thaw depth occurs to the embankment centric line has nothing to do with time, but is closely related to the surface materials, the embankment heights and strikes. Moreover, it is linearly related to the embankment heights. (3) Under the same embankment height and roadbed strike, the distance from the point where the maximum thaw depth occurs to the centric line of the embankment beneath the gravelly surface is larger than that beneath the asphalt surface. However, the maximum thaw depth beneath the asphalt surface is much larger than that beneath the gravelly surface. To some extent, the asphalt surface partially offsets the shadowy–sunny slope effect, but it makes the maximum thaw depth become much larger. (4) When designing an embankment, besides considering the minimum and the maximum embankment height, the shadowy–sunny slope effect also should be taken into account.