Research On Design And Temperature Effect Of Subgrade Cooling Pipe In Permafrost Regions

Because the global elevation of temperature causes permafrost to assume thedegenerated tendency, permafrost area embankment thermal stability has received thewidespread attention. In order to guarantee the embankment thermal stability; kinds oftreatment has been made to protect subgrade in permafrost area,such as block-stoneembankment, ventilated embankment, heat pipe subgrade etc.Due to the differentApplicable occasions to each treatment, inhomogeneous deformation, cracking andfrost boiling still are main problems to affect the service level of road in permafrostarea.This research proposed a new kind of treatment measure to special subgrade:cooling pipe subgrade treatment based on the present measures. The paper start withthe Geography&Weather characteristics in Qinghai-Tibet Plateau and modeling afinite element model based on fluid-solid coupling theory. Analyzed the distributioncharacteristics of thermal field in soil which is around the cooling pipe; Checked thecomputation result with model test in lab; Analyzed different influence factors to thecooling effect of the cooling pipe and proposed design philosophy and parameters ofthe cooling pipe.The result of this research shows that: environment temperature and soiltemperature are two main factors to the cooling pipe. Cooling effect of the coolingpipe is increasing with the flow of ventilation time,decreasing with the rise of soiltemperature, increasing with the diminution of environment temperature, increasingwith the rise of the air speed and pipe diameter. Along with the cross section,soiltemperature decrease with the distance to shell of pipe, Along the vertical section, thecentral position of the soil is the hardest part for cooling. The activated temperaturedifference is proved to be6℃.The recommended pipe diameter is0.3m~0.4m,Reasonable depth is1m~2.5m below natural ground, the space between two pipesshould be1.2m~1.6m.The activating condition is environment temperature（Te）≤0℃and soil temperature（T0）＞4.5℃during warm season，Te≤0℃and T0＞2.5℃ during cold season.