Prediction method of screw pile bearing capacity under uplift load

The screw threads continuously distributed along the surface of the pile significantly modify its bearing mechanism, distinguishing it from traditional column piles. Currently, methods for calculating the uplift bearing capacity of screw piles remain underdeveloped. This study presents a calculation method for the uplift bearing capacity of screw piles based on the segmented displacement coordination iterative method, as well as a prediction method for the ultimate uplift bearing capacity using the intersection convergence method. The accuracy of these methods was validated through model and field tests. Using these theoretical calculation and prediction methods, the uplift bearing characteristics and influencing factors of screw piles were analyzed. The results demonstrated that the unique screw thread structure of screw piles significantly enhances their uplift bearing capacity compared to column piles. The P-s curve of screw piles exhibits a slow variation characteristic, and under ultimate bearing state, the shaft resistance is primarily provided by the deeper soil layers. The ultimate uplift bearing capacity of screw piles rises initially and declines as the screw pitch increases, reaching its maximum value when the screw pitch equals the second critical screw pitch. Furthermore, as the internal friction angle increases, screw piles outperform column piles more significantly in uplift capacity.