With globe warming,road safety will change dramatically,especially within the Qinghai-Tibet Plateau permafrost regions.Because of higher elevation and better atmospheric transparency,the Qinghai-Tibet Plateau has stronger radiation than other regions,which can change the daily variation of ground surface temperature on the Plateau.The awning measure(shading board) is one of the actively protected permafrost measures,which was adopted along the Qinghai-Tibet railway and highway and the Qing-Kang Highway in China.Field test results show that embankment surface month mean net radiation is 60-130 W/m2,but the value is below 20 W/m2 under the shading board,and the reducing level of natural net radiation is 80%-90%.The shading board reduced the heat flow entering into the embankment by 80%-90% or more,with heat entering into the soil on the common embankment,but emitting from the embankment under the shading board.At the same time,ground surface temperature under the shading board is 6-8 ℃ lower than the exposed embankment.Test results show that the shading board measure can rapidly and effectively reduce net radiation and heat flow into the embankment,decrease embankment surface and interior temperature,effectively delay increase rate of soil temperature under globe warming,ensure stability and safety of the embankment,and guarantee unblocked road projects in cold and permafrost regions.
