多年冻土区热棒路基应用效果
Applicable effect of thermosyphon subgrades in permafrost regions

为了研究热棒在青藏公路多年冻土区的应用效果,基于楚玛尔河试验监测场地8年的地温观测数据,以水平温度梯度为指标,分析了不同时期热棒的有效半径。为了提高热棒的调控效果,拓展热棒的使用范围,满足宽幅路基强吸热的使用要求,依托北麓河与安多2个试验监测场地,分析了热棒-XPS板路基与热棒-片块石路基地温监测数据。分析结果表明:热棒工作1年后的有效半径约为2.3 m,此后,随着热棒工作时间的增加,热棒影响范围逐渐增大; 在热棒工作的前5年,地温降幅明显,周围土体地温降幅都基本维持在0.5 ℃以上,之后每年降温较小,这主要是由于外界环境温度升高,气温与地温的温差逐渐减小,热棒工作的动力逐渐衰减引起的; 在热棒工作的8年中,由于热棒的持续制冷作用,热棒路基的人为上限基本不变,而普通路基同时期人为上限最大降低约为80 cm; 热棒-XPS板路基从6月份开始,XPS板上下温差不断增大,最大温差约为17 ℃,有效阻隔了暖季大量热量向板下传递; 热棒-片块石路基通过2年的调控作用,地温最大降幅为0.51 ℃。
In order to investigate the applicable effect of thermosyphon in permafrost regions along Qinghai-Tibet Highway, 8 years’ observational ground temperature data were collected from Chuma’er River test site, and the effective radius of thermosyphon was evaluated by taking the horizontal temperature gradient as the index. Additionally, to enhance the temperature-adjusted effect of thermosyphon, extend its application scope and meet the using demand of strong heat absorption of widened subgrade, the observational ground temperature data of the subgrade with XPS insulation board and thermosyphons and the subgrade with rock-crushed interlayer and thermosyphons at Beilu River and Anduo test sites were analyzed. Analysis result shows that the effective radius of thermosyphon after 1 year’s operation is about 2.3 m, and the influencing range gradually increases with the increase of operational time. Within the first 5 years of thermosyphon operation, the ground temperature obviously decreases, the ground temperature’s decreasement around the thermosyphon is over 0.5 ℃, and then, the ground temperature slowly decreases, which results from the decrease of ground-air temperature difference because of the increase of air temperature and the gradual decay of work motivation of thermosyphon. During 8 years of thermosyphon operation, the artificial permafrost tables of thermosyphon subgrades are almost unchangeable because of thermosyphons’ continuing refrigeration, while the maximum decrease of contemporaneous artificial permafrost table of common subgrade is about 80 cm. Since June for the subgrade with XPS insulation board and thermosyphons, the temperature difference between top and bottom of XPS insulation board gradually increases, and the maximum value is 17 ℃, which effectively mitigates the downward transfer of heat in warm seasons. In 2 years’ adjustment of subgrade with crushed-rock interlayer and thermosyphons, the maximum decrease of ground temperature is 0.51 ℃. 16 figs, 25 refs