Abstract
In order to improve the thermal stability of wide embankment for the Qinghai-Tibet Expressway (QTE) to be constructed in permafrost zones on Qinghai-Tibet plateau, a new kind of reflective-resistant-ventilated coupling structure (RRVCS) was proposed and designed. A numerical model was then developed through ABAQUS to investigate the influences of RRVCS on the thermal regime of wide embankment. The temperature field and thawing depth of normal wide embankment without protective measures, wide embankment with crushed stone layer, and wide embankment with RRVCS were compared to verify the cooling effectiveness of RRVCS based on numerical analysis. Vermiculite powder has great influences on the thermal property of asphalt mixture, and it can be reduced by 22.8%, 29.5%, 37.3%, and 50.6% after the addition of 4%, 6%, 8%, and 10% vermiculite powder, respectively. Under the same condition, the temperature of RRVCS embankment is the lowest and its thermal stability is the best. Setting crushed stone layer can improve the thermal stability of embankment. However, the improvement is limited for wide embankment with width exceeding 26 m. RRVCS has the best protective effects on the thermal stability of wide embankment and is recommended as a protective measure for wide embankment of expressway in permafrost regions of Qinghai-Tibet Plateau.
Highlights
As the first expressway connecting Tibet to other provinces in China, the Qinghai-Tibet Expressway (QTE) will be constructed on the Qinghai-Tibet Plateau in accordance with the China National Expressway Network Plan [1]. e construction of QTE is of great importance because it can eliminate traffic bottlenecks in Tibetan areas and promote China’s social and economic development
Based on the nite element software ABAQUS, a numerical model was built to simulate the temperature eld of wide embankment and evaluate the e ectiveness of re ective-resistant-ventilated coupling structure (RRVCS) to improve the thermal stability of wide embankment. Another conventional cooling method crushed stone layer, was selected for comparison. e in uences of di erent protective measures on the temperature eld and thawing depth of underlying permafrost of wide embankment were investigated based on numerical analysis
Erefore, a re ective-resistant-ventilated coupling structure (RRVCS) was proposed in this study. It consists of three parts: re ective coating, heat-resistant pavement, and crushed stone embankment. e cooling e ect of RRVCS includes the following: (1) the re ective coating would increase the albedo of road surface and decrease the solar radiation absorbed by asphalt pavement; (2) the heat-resistant pavement could impede the heat transferring downward, reducing the heat conducted to the frozen soil; and (3) the crushed stone embankment can dramatically release heat accumulated in permafrost embankment according to the Rayleigh–Bernard convection mechanism [18]
Summary
As the first expressway connecting Tibet to other provinces in China, the Qinghai-Tibet Expressway (QTE) will be constructed on the Qinghai-Tibet Plateau in accordance with the China National Expressway Network Plan [1]. e construction of QTE is of great importance because it can eliminate traffic bottlenecks in Tibetan areas and promote China’s social and economic development. Because of climate warming and human activities, the permafrost in this area could thaw and lose its bearing capacity, leading to activelayer detachment failure, thaw subsidence, and failure of many other geohazards [7] To address these issues, much effort has been exerted by researchers all over the world and a number of measures to cool down permafrost subgrade have been devised, including crushed stone embankment, thermosyphons, air-cooling ducts, awnings, insulating materials, raising the embankment height, and combinations of these methods [8,9,10,11,12]. Based on the nite element software ABAQUS, a numerical model was built to simulate the temperature eld of wide embankment and evaluate the e ectiveness of RRVCS to improve the thermal stability of wide embankment Another conventional cooling method, namely, crushed stone layer, was selected for comparison. Another conventional cooling method crushed stone layer, was selected for comparison. e in uences of di erent protective measures on the temperature eld and thawing depth of underlying permafrost of wide embankment were investigated based on numerical analysis
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