Abstract：To analyze refreezing of frozen ground and its influence on foundation stability in the Qinghai-Tibet DC Transmission Line Engineering，temperature monitoring for a freezing-thawing process is carried out for the assembling prototype foundations and frozen soil in Wudaoliang area on the Tibetan Plateau. Combining with atmospheric temperature data in the area，the ground temperature changing characteristics with time and distributing along the depth of undisturbed and backfill coarse-grained frozen soil are analyzed. Monitoring results show that：(1) Ground temperature is periodic fluctuation and its amplitude decreases with increase of depth. There is a freeze-thaw state alternating layer in the upper undisturbed and backfill soil. (2) In the monitoring period，the frozen soil below foundation slab is in frozen state and the foundations are stable. (3) The maximum thawing depths of undisturbed and backfill frozen soil are 3.0 and 3.2 m respectively. Through the establishment of ground temperature estimation formula，and based on the results of ground temperature change amplitude and mean value，etc.，it is obtained that the permafrost table is 3.1 m，which is consistent with the results of engineering survey and monitoring. (4) Using heat transfer theories，ground heat transfer model of high porosity frozen soil backfilled in winter is established. The heat transfer ability and air natural convection velocity effects on refreezing of ground are analyzed. The results indicate that：(1) Backfill disturbance of frozen soil aggravates temperature fluctuation amplitude and increases the thawing depth，but the effect degree and range are limited. (2) Construction of transmission lines in frozen soil and assembly foundations in winter and keeping proper porosity of the backfill frozen soil in freeze-thaw active layer are beneficial not only to accelerate the ground refreezing，but also to increase compaction degree because of soil natural consolidation and thawing settlement. So，the frozen state in the warmer seasons could keep while heat diffusion to deeper ground weakens.
程永锋1，丁士君1，鲁先龙1，谭 蓉2. 青藏直流输电工程粗粒冻土地基温度监测与分析[J]. 岩石力学与工程学报, 2012, 31(11): 2363-2371.
CHENG Yongfeng1，DING Shijun1，LU Xianlong1，TAN Rong2. MONITORING AND ANALYSIS OF COARSE-GRAINED FROZEN
SOIL TEMPERATURE IN QINGHAI-TIBET DC
TRANSMISSION LINE ENGINEERING. , 2012, 31(11): 2363-2371.
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2012, Vol. 31 
