Influence of slope orientation on the near-surface hydrothermal state of roadbed slopes in high-altitude permafrost areas
The difference of slope aspect in high altitude permafrost region may cause the asymmetry of tempera-ture field on the two slopes,and then cause uneven settlement and longitudinal cracks of infrastructure.At pres-ent,the research on the influence of slopes mainly focuses on the monitoring and simulation of the east and west slopes of the Qinghai-Xizang Railway,seldom on the other slopes.But the trend of the linear project in plateau may involve different directions,we cannot promise the railway always in one orientation in the linear engineer-ing and the research on the status of the water and heat difference on other slope aspects is insufficient.In this study,to found a relationship of soil temperature and moisture content in Qinghai-Xizang Plateau,and study the influence of the different slopes.A monitoring entity with eight directions(known as an octagonal platform)was built in the Huashixia permafrost station,the base of the observation of the frozen soil in Qinghai-Xizang Plateau.Soil temperature and moisture content sensors were installed on the meddle of eight slopes in(10 cm,20 cm,30 cm)3 depths near the surface and the top surface.To monitor and study the impact of slope aspect differences on the state of water and heat on the slope near surface.The results shew that the difference of the near surface temperature on the east to west slope was the smallest,the monthly average temperature difference from 0.1℃to 2.3℃,and in this difference,the maximum temperature difference occurs in May;The tempera-ture difference near the surface of the south to north slope was the largest,with the monthly average temperature difference of 1.3℃to 7.7℃,and the maximum temperature difference occurs in February in this temperature difference.The remained near surface temperature difference of the other two relative slopes was between the east-west slope and south-north slope,and the temperature difference of the northeast-southwest slope was small-er than that of the northwest-southeast slope.From the perspective of temperature difference near the surface of slope,the north-south,whose thermal stability of linear engineering in high altitude permafrost region is better,followed by the northwest-southeast direction,the influence of slope was not significant and the temperature field was symmetrical.Similarly,the overall difference of near surface soil moisture content of the eight slopes,whose data came from 3 depths like the near surfaced soil temperature,and the device of the sensors was the same to the soil temperature,which was the smallest in the orientation of northeast-southwest,and the maximum monthly average moisture content difference was 0.06 m3·m-3 during the melting period;The east-west slope sur-face difference was the largest,and the maximum monthly average water content difference in the same period was 0.11 m3·m-3 This difference seemed on the opposite of the soil temperature.The difference of temperature and moisture content also causes a significant difference in the number of freeze-thaw cycles on different slopes,which has an important impact on the freeze-thaw damage of slope protection materials with rubble.In this re-search,south slope,whose freeze-thaw cycles times was the top one and higher than the west slope to 88 times,other slopes like east and northwest were close to 60 times,north slope and northeast slope were higher than west slope and northeast was higher than north.In this time,freeze-thaw cycles time in the top surface was the third high in all the slopes.The research results have a certain guiding significance for the future plateau linear engi-neering planning and the treatment of the different diseases of the solar and lunar slopes of the existing projects.
high altitude permafrostlinear engineeringinfluence of slope orientationnear surface tempera-turenear surface moisture content
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