Thermal regime of frozen soil foundation affected by concrete base of transmission line tower on the Tibetan Plateau

• A 3-D model of frozen soil foundation of concrete base with phase change and internal heat source is presented.
• The thermal regimes of frozen soil foundation affected by concrete base constructed by two different methods were investigated.
• Cast-in-place concrete base has great heat influence on the frozen soil foundation.
• Fabricated construction method is proposed in the concrete base construction in permafrost regions.

Frozen soil is so sensitive to the temperature change. The melt of ice in soil can lower the bearing capacity of foundation. This work aims to investigate the thermal regime of the frozen soil foundation, affected by transmission line tower concrete base which is constructed by two different methods. One is the cast-in-place construction method; another is the fabricated construction method. A three-dimensional model is developed to predict the thermal regime of the frozen soil foundation and the concrete base, considering the hydration heat of concrete. The phase change between water and ice is considered by using the sensible heat capacity method. The results show that the concrete base constructed by the cast-in-place method has great influence on the thermal regime of frozen soil foundation in about one month after the base constructed. The soil surrounding the base experiences severe melting-freezing process in this period. In first four months, the thaw progressing of the two construction cases is significant different. For the cast-in-place construction case, the heat influence area on the frozen soil is along the base side. But for the fabricated construction case, it is only in the active layer. And then, the reasonable construction methods are recommended.