Displacement Pile Group Efficiency Assessment for a Technically and Economically Sustainable Design of Pile Groups in Non-Cohesive Soil

Motivated by field investigations on driven precast piles, this paper presents the results of large-scale physical test series involving a 3 x 3 displacement pile group with a pile spacing of 3∙D in medium-dense sand. Additionally, a concurrent single pile test was performed to enable direct comparison under identical conditions. Three of the group piles were equipped with strain gauges to evaluate group effects on the mobilization and distribution of skin friction and tip resistance. Besides, pile head forces were measured to determine the load distribution inside the pile group. Soundings with the dynamic PANDA®-penetrometer within the pile group were performed to investigate compaction effects due to pile installation. Based on the findings from the test program, various types of settlement-related efficiencies for design purposes can be derived, including 3 x 3 pile group efficiency, group pile efficiencies, as well as skin and tip efficiencies.