Thermal effect of backfill material on the refreezing process of power transmission line cone-cylindrical foundation in permafrost regions

As the backfill material is directly in contact with the foundation, its heat transfer characteristics determine the overall safety of the foundation. In this regard, a novel study on the refreezing process of backfill soil based on model tests and numerical simulations is presented in this paper. The model test results showed that the higher the density of the backfill soil, the shorter the refreezing time of the soil and the refreezing time of the models was 14 d, 22 d, and 39 d. Numerical simulation results proved the correctness of the model tests. At the same time, the initial temperature of the backfill has little effect on the refreezing process of the backfill under real conditions. Increasing the density of the backfill could shorten the refreezing time of the backfill to a maximum of 11.5 d. The selection of different types of backfill soil could shorten the refreezing time to 19 d. This research recommends that the reasonable selection of backfill materials under the condition of strictly controlling the density of backfill soil is beneficial to speed up the process of refreezing the transmission line tower foundation.