An experimental study on the cooling mechanism of a shading board in permafrost engineering

Yu, Qihao; Xiong, Pan; Guodong, Cheng; He, Ning

doi:10.1016/j.coldregions.2007.07.003

Cited by 39 publications

(10 citation statements)

References 3 publications

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“…1). Details for the stratum in this site can be referred to previous works Yu et al 2008b). The DK1136?755 section is an earthen roadbed, which was intentionally designed without the protection of any proactive cooling measures.…”

Section: Field Observationmentioning

confidence: 99%

“…The methods may include individually or in combination: (1) shading boards (Feng et al 2006;Yu et al 2008b), (2) crushed rock layers (Li et al 2008;Niu et al 2006;Niu et al 2008), (3) thermosyphons (Wen et al 2005;Wu et al 2010), (4) ventilation ducts (Yu et al 2008a), and (5) land bridges (Cheng et al 2008). These techniques cool the underlying permafrost by increasing the heat loss at the roadbed surface whereas maintaining or even decreasing the heat gain from the surrounding air.…”

Section: Introductionmentioning

confidence: 99%

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Permafrost warming under the earthen roadbed of the Qinghai–Tibet Railway

Qin

2011

Environ Earth Sci

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This paper investigates the stability of the earthen roadbed built in the warm and ice-rich permafrost region. The varying thermal regime of the subgrade and the ongoing settlement of the roadbed were observed at field. The temperature data demonstrate that in warm and ice-rich permafrost regions, adoption of earthen roadbed results in warming of the underlying permafrost. It is primarily because the earthen roadbed traps the warm-season absorbed heat in the natural ground. In addition, the carried heat of the earthen roadbed that was constructed in warm season propagates downward to warm the underlying soil. The warming permafrost layer promotes the roadbed settlement, which was mostly linearly developed in the past five service years. A comprehensive analysis for the varying thermal regime and the ongoing settlement shows that the unfrozen water liberated from the warming, undrained layer experiences consolidation. The deformation of the undrained soils is mainly responsible for settlement of the roadbed. In comparison, the temperature variation of this warming permafrost layer is found to be less beneath roadbeds protected by thermosyphons or crushed rock revetments. The installation of thermosyphons into the earthen roadbed is recommended to prevent the further degradation of the underlying permafrost.

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Section: Field Observationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Permafrost warming under the earthen roadbed of the Qinghai–Tibet Railway

Qin

2011

Environ Earth Sci

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“…The temperature data measured from the inner walls of the ventilation ducts indicated that ducts with shutters were 1℃ colder than those without. The mean annual ground temperature measured at a depth of 3.5 m beneath the shuttered embankment showed that air ducts was 0.45℃ lower than that beneath the embankment installed with normal air ducts [25] .…”

Section: Ventilation Ductsmentioning

confidence: 99%

Innovative designs of permafrost roadbed for the Qinghai-Tibet Railway

Guodong

2008

Sci. China Ser. E-Technol. Sci.

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Under global warming scenarios, the passive method of simply increasing the thermal resistance by raising the embankment height and using insulating materials has been proven ineffective in warm and ice-rich permafrost areas and therefore could not be used in the Qinghai-Tibet Railway engineering. Instead, a proactive "cooled-roadbed" approach was developed and used to lower the ground temperature in order to maintain a perennially frozen subgrade. The concept that local and site-specific factors play an important role in the occurrence and disappearance of permafrost has helped us to devise a number of measures to cool down the roadbed. For example, we adjust and control heat transfer by using different embankment configurations and fill materials. The Qinghai-Tibet Railway project demonstrates that a series of proactive roadbed-cooling methods can be used to lower the temperature of permafrost beneath the embankment and to stabilize the roadbed. These methods include solar radiation control using shading boards, heat convection control using ventilation ducts, thermosyphons, air-cooled embankments, and heat conduction control using "thermal semi-conductor" materials, as well as combinations of above mentioned three control measures. This roadbed-cooling approach provides not only a solution for engineering construction in sensitive permafrost areas but also a countermeasure against possible global warming.warm permafrost, global warming, Qinghai-Tibet Railway, cooled roadbed

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“…Therefore, a numerical simulation for the thermal conditions of the embankment section located at the Beiluhe site can satisfy the investigation purpose. The geological details for this site can be referred to previous works (Ma et al 2008;Yu et al 2008).…”

Section: Numerical Modelmentioning

confidence: 99%

Effects of diurnal temperature rhythm on the geothermal regime under the embankment in Qinghai–Tibet plateau

Qin

Tang

2010

Arab J Geosci

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The objective of this study was to investigate the effects of diurnal temperature fluctuation amplitude (DTFA) on the geothermal regime of the embankment on the Qinghai-Tibet plateau. The investigation was simulated by respectively denoting the diurnal temperatures at the embankment surface, embankment slope, and natural ground surface with sinusoidal waves. The amplitudes of the waves were denoted by 0°C, 5°C, 8°C, and 12°C, respectively. The numerical result shows that the DTFA cannot vary the frequency of the seasonal temperature fluctuation of the underlying soil, but can significantly change the magnitude of the soil's temperature. The changes include: (1) The high DTFA, such as 12°C, can significantly lead to the warming of the soil under the embankment. (2) Interestingly, when the DTFA at ground surface is 5°C, the underlying soil is in a cooler stage compared to when such DTFA is 0°C, 8°C, or12°C. This interesting result means that the documented model which ignores the diurnal temperature rhythm overestimates the warming of the underlying soil at the low DTFA region and underestimates such warming at the high DTFA region. This result also suggests that the soil under the embankment can be cooled down if the DTFA on the ground surface was maintained at or approximately at 5°C.

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An experimental study on the cooling mechanism of a shading board in permafrost engineering

Cited by 39 publications

References 3 publications

Permafrost warming under the earthen roadbed of the Qinghai–Tibet Railway

Permafrost warming under the earthen roadbed of the Qinghai–Tibet Railway

Innovative designs of permafrost roadbed for the Qinghai-Tibet Railway

Effects of diurnal temperature rhythm on the geothermal regime under the embankment in Qinghai–Tibet plateau

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