Abstract: Compared with the common soils, frozen soils have unique engineering properties. After the pile foundation was constructed in regions with polygonal permafrost, the frozen soil and pile sustain the load as an integral due to the cementing effect between pile and surrounding frozen soil in the refreezing process. In order to obtain the properties of capacity and deformation before and after refreezing process, two 15 m testing piles were constructed in Daxinganling, China. Temperature monitoring system was adopted to record the temperature change in refreezing process. Based on the monitoring results, self-balanced static load test was conducted to determine the bearing capacity, tip and lateral friction within different stratus. The results show that the frozen soil was -1.9°C after refreezing. The capacity is 1.42 times of that before refreezing, and the tip friction is 1.49 times of that before freeing, which consisted about 12.98% of the total pile capacity. The average increment in pile lateral friction is 40.3%. This paper can serve as an evidence for the pile design and construction in permafrost areas.

Key words: patchy permafrost, pile foundation, temperature, soil freezing, self-balanced load test, bearing capacity