通风路基主要影响因素及应对措施研究

STUDY ON MAIN INFLUENTIAL FACTORS ON VENTILATED EMBANKMENT AND CORRESPONDING MEASURES

结合实测资料,通过模拟计算从传热角度就通风路基降温效能的主要影响因素进行分析。研究发现,在管道通风路基中,管间土体存在较强的热流向下传热,通风管间距是影响降温效能的重要因素之一。在公路沥青路面条件下,由于路面的强烈吸热作用,通风路基的降温效能被极大削弱,环境升温和设计不当都可能造成工程措施的失效。针对这一问题,提出宽幅通风新型工程措施。模拟计算结果表明,该种新型路基具有高效、快速的降温效能。在沥青路面条件下,该种措施实施3 a后,-3 m深度的地温就已低于原天然地表下的温度,冻土人为上限在快速达到路堤底部约-0.5 m深度后,完全维持稳定。该种措施还成功解决路基地温场的非对称性难题,进一步增强路基的长期稳定。这些结果对我国多年冻土区高等级公路的建设和关键工程问题的解决具有重要意义。

Combining the collected data and numerical simulation,the main influential factors on ventilated embankment are analyzed in the light of heat transfer in permafrost engineering.It is found that there is a strong heat flux between the two adjacent ventilating pipes in the ventilated embankment;and the distance between the two adjacent pipes is one of the important factors influencing the cooling effects.This is proved by measured data.According to the measured data in Beiluhe test site along Qihai—Tibet Railway in Qihai—Tibet Plateau,in ventilated embankment testing field,the cooling effect with vent-pipe diameter 30 and 60 cm between the two adjacent pipes is better than that with diameter 40 and distance 80 cm.Because of the strong heat-absorbing action of black asphalt road,the numerical simulation shows that the heat flux between the ventilating pipes is much larger than that in the road with sand-soil surface;and the cooling effect of the ventilated embankment will be weakened,it can become invalid if the design is improper.With this situation,a creative method is suggested to enhance the embankment design.The numerical simulation of this ＂new style＂ embankment demonstrates its efficacy and quickness in cooling embankment.Three years after the development and application of this ＂new-style＂ embankment with an asphalt surface,the ground temperature at 3 m under center of embankment bottom surface appeared to be lower than that in the natural condition;and the entire permafrost table remains solid during the intended road′s service duration.The permafrost table quickly rises to 0.5 m under the embankment bottom.It effectively solves the asymmetry problem in the embankment thermal field.This can be also helpful in maintenance of the long-term stability of the embankment.These results have significant effects on highway design in permafrost regions.