青藏铁路多年冻土区电力杆塔热桩基础的降温效果分析

在热棒外围浇筑混凝土形成的热桩基础在冻土区电力杆塔中常被应用。热棒的工作功率随着大气温度、蒸发段土体温度的变化而变化。基于冻土传热学相关知识，结合青藏铁路望昆~不冻泉段电力杆塔基础的现场地温测试试验，建立热桩基础的三维有限元模型。考虑全球气候变暖、冻土相变、混凝土水化放热、热棒功率变化等因素，运用迭代的方法进行热棒功率和桩周土体温度计算。计算结果表明：计算结果与实测结果吻合程度较高，能较好的模拟现场情况。热棒的功率呈非连续波浪式变化，受混凝土入模温度及水化放热的影响，初始阶段功率达到最大160.6 W，第2年的平均功率比第1年低7.0 W。热桩基础能够有效增加基础冷储量，最大降低桩侧土体地温2.1~3.0℃，年平均地温降低0.8~1.5℃，能缩短桩周土体回冻时间约34%，第30 a可提高冻土上限49 cm。

The cooling effect of power tower thermosyphon foundation in permafrost regions of the Qinghai-Tibet Railway

The thermosyphon foundation formed by pouring concrete around the thermosyphon is often used in power tower in frozen soil regions. The working power of the thermosyphon varies with atmospheric temperature and soil temperature by the evaporation section. A three-dimensional finite element model of thermosyphon foundation was established in this paper, which based on the knowledge of frozen soil heat transfer and the field test of ground temperature of power tower foundation in the Wangkun-Budongquan Section of the Qinghai-Tibet Railway. Considering the global warming, frozen soil phase change, hydration heat release of concrete and the change of thermosyphon power, the thermosyphon power and the soil temperature around the pile are calculated by iterative method. The calculation results show that the calculated results are in good agreement with the measurement and can reasonably simulate the actual situation in the field well. The power of the thermosyphon varies with discontinuous wave, and the power in the initial stage is up to maximum 160.6 W, and the average working power in the second year is 7.0 W lower than that in the first year due to the influence of the temperature of the concrete entering mold and the hydration heat releasing. The thermosyphon pile foundation can effectively increase the cold reserves of the foundation; the maximum reduction of soil temperature may reach 2.1~3.0 ℃ and the average annual ground temperature can decrease 0.8~1.5 ℃. It also can shorten the soil refreezing time by 34% and will increase the permafrost table by 49 cm in the thirtieth year.