Comparison of vertical and shallow angled raked piles under lateral load

This report gives the results of field loading tests carried out on vertical and shallow-angle raked, bored cast-in-place piles founded in London Clay. The piles were 0.17 m in diameter and had embedded lengths of 4.5 m. During the tests increasing levels of static and cyclic lateral load were applied to a single vertical pile, a single pile raked at 10 degrees, a bent of vertical piles and a bent of one vertical and one raked pile (10 degrees). The effect of the loadings on the performance of the piles under lateral and vertical loads was examined. The below-ground deformations of the piles and the loads in the piles were monitored by instruments developed by BRE. The information obtained enabled the performances of the piles under lateral load to be compared in terms of deflections, bending moments and soil reactions and under vertical load in terms of deflections and load distribution in the piles. Instruments installed in the soil close to the piles enabled in-situ estimates to be made of the soil stiffness. The procedures for processing the information obtained from the new instruments into pile performance and soil data are outlined. The results from the investigation were used to assess several design procedures for laterally loaded piles. Three linear elastic and one non-linear (p-y) computer based analysis methods were assessed. The elastic methods varied from a relatively sophisticated finite element package that allowed the soil to be modelled using 8 different stiffnesses that could be varied both radially and with depth, to simpler methods that only allowed stiffness variations with depth. Soil parameters determined directly from the instrumentation.