Correction calculation method for axial force distortion of cast-in-place piles in permafrost regions considering non-load deformation

It is a conventional method for pile monitoring to calculate axial force and shaft resistance indirectly according to the values measured by the rebar strain meters which are embedded in piles. However, the measured values from the rebar strain meter include the stress caused by the load applied to the pile foundation and the additional stress caused by various non-load factors. Therefore, it is rather questionable to estimate the concrete stress according to the ratio of elastic moduli between steel bars and concrete, especially in permafrost regions. Based on the actual material properties of reinforced concrete piles and consistency conditions, several equations are established considering the temperature-induced deformation, frost-heave deformation, dry shrinkage and wet-swelling deformation, autogenous deformation, creep deformation of pile concrete, and temperature-induced deformation of steel bars. Considering the non-load deformation, the load-induced stresses of concrete and steel bars of the cast-in-situ piles in permafrost regions are obtained. Finally, the axial force and shaft resistance caused by the actual load are calculated. The results show that the proposed method is reasonable and effective. The new method can avoid axial force distortion and the unreasonable results caused by the traditional method due to non-load deformation. Hence, the proposed method is of practical significance for the bearing performance analysis of pile foundations.