Field test study on uplift bearing characteristics of rock socketed piles in sandstone stratum

Based on the field ultimate load test, the uplift bearing characteristics of reinforced cement concrete (RCC) bored piles in clay and sandstone strata were analyzed, and semi empirical methods for calculating the ultimate uplift capacity of rock socketed pile were proposed. This method was compared with the design codes of pile foundations in China and Europe, and its reliability was verified by engineering case analysis. The results show that the relationship curves between pile top displacement and uplift load are of steep deformation type. In the field test, the ultimate uplift capacity increases with the increase of rock socketed depth or pile diameter. The failure mode of uplift pile is the relative sliding failure of pile body and surrounding rock and soil. In this technical report, the relationship between ultimate side resistance f r and unconfined compressive strength σ c of sandstone is proposed, f r = 0.18 σ c 0.5 (MPa). And the calculation method of ultimate uplift capacity of the pile in clay and sandstone strata is proposed. The calculated results are in good agreement with the test results, with an error of −11.4 % to 9.5 %, which is smaller than that of the design codes of pile foundations in China and Europe. This calculated method has a certain reference for the design of uplift piles in similar strata.