Abstract: In recent years, accidents caused by horizontal frost heave frequently occur in foundation pit projects over winter in seasonally frozen soil areas, but there are few researches on anti-frost heave measures. In this paper, the field monitoring of foundation pits over winter of pile-anchor supporting structures in Changping District of Beijing is carried out, and the evolution law of frost heave characteristics such as soil moisture migration, stress state of supporting structure and horizontal displacement of slope protection pile is analyzed. A hydro-thermal coupling model is established, and the model is verified by comparing the results with the monitoring data. Taking the temperature field distribution, horizontal displacement of slope protection pile and horizontal frost heaving force of supporting structure as indexes, using numerical calculation results, the suppression effects of insulation layer and replacement of non-frost heaving soil and setting parameters on horizontal frost heaving are compared, and the effective anti-frost heaving measures are put forward. Studies have shown that the freezing of foundation pit soil is caused by the combined action of vertical and lateral water migration; the inhibition effect of laying an insulation layer on frost heaving is significantly better than replacing non-frost heaving soil. Laying an insulation layer is recommended to be used in projects since it is more economical, feasible and easier to operate. The research results can provide theoretical support for the design and construction of supporting structures in cold areas in the future.

Key words: foundation pit over winter, horizontal frost heave, pile-anchor retaining structure, thermal-hydro-mechanical coupling, frost heave measures