Study on the horizontal bearing mechanism of stepped variable cross-section piles

ObjectivesThis study aims to investigate the horizontal bearing mechanism of rigid and elastic stepped variable cross-section piles in silty sand foundations and to evaluate the impact of variable diameter factors on horizontal bearing capacity. Indoor and numerical simulation experiments were conducted.MethodsHorizontal loading tests were performed on rigid and elastic stepped variable cross-section piles as well as constant cross-section piles. Finite element software was used to develop numerical models with different variable diameter ratios and lengths for analysis.ResultsThe results indicate that reducing the diameter of the lower half of the pile， using the stepped variable cross-section design， has a minimal impact on the horizontal bearing capacity of the elastic piles. Considering material efficiency， the unit volume horizontal bearing capacity of the rigid stepped variable cross-section pile is 6.4% higher than that of the constant cross-section pile， while the elastic stepped variable cross-section pile shows a 33.28% increase. Under the same horizontal load conditions， the shallow soil resistance of the rigid stepped variable cross-section pile is higher than that of the constant cross-section pile， while the shallow soil resistance of the elastic stepped variable cross-section pile is lower than that of the elastic constant cross-section pile. The horizontal bearing capacity of the stepped variable cross-section pile increases with higher variable diameter ratios and lengths， while the unit volume horizontal bearing capacity decreases as the variable diameter ratio increases. When the variable diameter ratio is 0.8 and the variable diameter length is 50% of the pile length， the horizontal bearing capacity of the elastic stepped variable cross-section pile is close to that of the elastic constant cross-section pile. Compared to the elastic constant cross-section pile， the unit volume horizontal bearing capacity is maximized when the variable diameter ratio is 0.8 and the variable diameter length is 40% of the pile length.ConclusionsThe unit horizontal bearing capacity of the stepped variable cross-section pile is higher than that of the constant cross-section pile. Reasonable optimization of the variable diameter length and ratio can help reduce project costs. The findings provide valuable insights for the application of stepped variable cross-section piles in practical engineering.