There is a paucity of systematic experimental studies on the group effect of dragloads in pile foundations. This paper reports on a series of 1-g model tests that were conducted on single piles as well as 2 × 2 and 3 × 3 pile groups with various pile spacings to investigate the influence of soil compressibility, pile installation method, pile end constraint, and pile spacing on dragload development in the piles. The results indicate that soil compressibility significantly influences the magnitude of dragloads developed in single piles and piles in a group. However, the effect of soil compressibility on the group effect (a measure of dragload reduction) is negligible. Pile spacing is the most significant factor that influences group effect, followed by the number and position of piles. The group effect can reach 50% for a spacing of 3D (where D denotes pile diameter), but becomes negligible for a spacing of 7D. The influence of pile end constraint and pile installation method on group effect is comparatively insignificant. Although group effects of the suspending piles are marginally lower than those of end-bearing piles under otherwise identical conditions, the dragloads on the suspending piles correspond to tensile forces and are detrimental to concrete piles.

对于桩基础中的荷载群效应，缺乏系统的实验研究。本文报告了一系列针对单个桩以及不同桩距的2×2和3×3桩组进行的1-g模型试验，以研究土壤可压缩性，桩安装方法，桩端约束，和桩间距对桩的拖曳力发展的影响。结果表明，土壤可压缩性显着影响单个桩和一组桩中产生的阻力。但是，土壤可压缩性对群效应的影响（减载的量度）可以忽略不计。桩距是影响群效应的最重要因素，其次是桩的数量和位置。对于3D的间距（其中D表示绒头直径），群效应可以达到50％，但是对于7D的间距，则可以忽略。桩端约束和桩安装方法对群效应的影响相对较小。尽管在其他条件相同的情况下，悬浮桩的群效应略低于端承桩的群效应，但悬浮桩上的曳力对应于拉力，并且对混凝土桩有害。