Effects of soil nonlinearity on the active length of piles embedded in cohesionless soil: model studies

Dynamic experimental studies on the active lengths of a fixed-head floating pile under static and dynamic loading conditions are reported, focusing on the effects of local nonlinearity and resonant behavior of soil. Results obtained from the laterally loaded model soil-pile system subjected to low-to-high amplitude pile head loading suggest a strong influence of local nonlinearity on the active lengths of the pile. Such obtained experimental results are further compared with the available approximate equations for estimating the active lengths. The comparisons reveal the closeness in values for very low amplitude of loadings, but for intermediate-to-high amplitude of loadings, the experimental values are smaller than predicted by the approximate equations. Moreover, both the static and dynamic active lengths of the pile converge to an approximately identical value of six times the diameter of the pile for intermediate-to-high amplitude of loadings. This suggests that the active lengths of the pile are, in fact, the same for both the static and dynamic loadings, under nonlinear conditions. Additionally, results also suggest that the passive-type failures of soil induced by the applied lateral loadings in front of the pile govern the active lengths. Furthermore, the dynamic active lengths of the pile do not show any significant dependency on the resonance in the soil.