U型块石路基结构对多年冻土的降温作用

The Cooling Effect of U-Type Crushed Rock Embankment on Permafrost

通过对比北麓河试验段U型块石路基结构和普通路基下部土体温度监测研究,U型块石路基显著地抬升路基下部多年冻土上限,具有较强的降低多年冻土温度的作用.2005—2007年间,U型块石路基下多年冻土上限平均抬升幅度达0.9~1.4 m.路基中心下部0.5 m深土体温度降温幅度达1.13℃,原天然上限附近土体温度降温达1.28℃,5 m深的多年冻土降温幅度达0.77℃,且U型块石路基下部土体温度呈现逐年降低的趋势.然而,普通路基下部土体温度远比U型块石路基下部要高,2005年普通路基下部0.5 m深土体年平均温度比U型块石路基高1~3℃,1.5 m处高0.8~1.9℃,5 m处高1.2~1.5℃.同时,U型块石路基下部多年冻土上限抬升比普通路基大,2004—2006年间U型块石路基左路肩下多年冻土上限抬升比普通路基大0.86 m,路基中心大0.5 m.

Based on the research on the ground temperatures within an ordinary embankment and a U-type crushed rock embankment,it is found that the U-type crushed rock embankment has a predominant effect of cooling permafrost and rising permafrost table.The average value of rising permafrost table was about 0.9 to 1.4 m from 2005 to 2007.The value of decreasing annual mean ground temperature was about 1.13 ℃ at the depth of 0.5 m,1.28 ℃ at the depth of 1.5 m near original permafrost table,and 0.77 ℃ at the depth of 5 m from 2005 to 2007.Ground temperature under the U-type crushed rock embankment shows a decreasing tendency from year to year.However,ground temperature under an ordinary embankment is much higher than that under a U-type crushed rock embankment.Annual mean ground temperatures at the depth of 0.5 m,1.5 m and 5.0 m beneath an ordinary embankment were 1 to 3 ℃,0.8 to 1.9 ℃,and 1.2 to 1.5 ℃ higher than those beneath a U-type crushed rock embankment in 2005,respectively.While,rising of permafrost table beneath a U-type crushed rock embankment is larger than that beneath an ordinary embankment.Rising of permafrost table under a U-type crushed rock embankment was 0.86 m and 0.5 m larger than that beneath an ordinary embankment for the left shoulder and for the center of embankment,respectively,from 2004 to 2006.