Hydro-thermal disturbance and its impact on the bearing characteristics of bored piles in ice-rich permafrost

Abstract

In warm, ice-rich permafrost regions, road construction confronts challenges such as frost heave, thaw settlement. Bored piles were first extensively utilized in the construction of the Qinghai-Tibet Railway. However, the effects of hydro-thermal disturbance—primarily from curing hydration heat—on the surrounding frozen soil, and its impacts on pile bearing characteristics post-refreezing, remain unclear. In this study, frozen soil’s melting-refreezing process, alongside associated moisture migration and redistribution is investigated via model experiments. By analyzing extensive field test data, how the thermal disturbance history influences the bearing characteristics of bored piles is further examined. Based on these findings, a hydro-thermal interaction mechanism between pile and surrounding frozen soil is proposed. Results indicate that thermal disturbance instigates the melting of upper ice layer, with moisture percolating downward into the soil pores along the thawed zone due to gravity. Upon refreezing, gaps at pile-ice interface and ice reallocation in the surrounding soil influence the distribution of shaft resistance. The study also reveals that pile diameter-determining the total hydration heat emission, together with the temperature and ice content of the adjacent permafrost—both impacting the thermal disturbance intensity and thawing extent, jointly shape the hydrothermal process of the pile-soil system. Higher moisture content in the soil tends to diminish shaft resistance, while larger pile diameters and higher ground temperatures augment end resistance ratio. The conclusions furnish a theoretical basis for designing and constructing bored piles in permafrost regions.