科研之友
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摘要
In order to study the overall refreezing process of ground temperature of transmission line foundation in different seasons and the disturbance characteristics of construction on permafrost in different seasons, the construction period of large-scale excavation type foundation was optimized from the perspective of maintaining ground temperature stability of permafrost. Based on the Qinghai-Tibet DC power transmission project, this paper uses the geological and meteorological data of Chalaping area and the typical months (January, April, July and October) are selected to calculate and analyze the early ground temperature field of cone-cylindrical foundation after construction in different seasons. The results show that after the construction in autumn and winter (October and January), the soil around the cone-cylindrical foundation will remain frozen, and the temperature difference between the soil in the backfill area and the natural frozen soil can disappear within ten d after the construction in January, and the thermal disturbance of the backfill soil is small. Construction in spring and summer (April and July) will increase the depth of the active layer and the thawing depth of permafrost during the thawing period, especially the construction in July can reduce the depth of active layer to the basement (4.0 m), while the construction in April can increase the temperature of the backfill soil and lead to the refreezing time is as long as 195 d which is not conducive to the refreezing of the backfill and the development of follow-up work. Considering that the outside temperature gradually decreases after October, October to January in the next year can be used as the best construction period for the cone-cylindrical foundation in the permafrost region.
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