扭转群桩中的阴影效应

Shadowing effect in pile groups subjected to torsion

通过离心模型试验对扭转群桩中的阴影效应进行研究。试验结果表明,受扭转荷载的大型群桩中存在着显著的阴影效应,导致群桩承载力的显著降低。阴影效应随着群桩布局和基桩位置不同而变化,1×2和2×2群桩中的阴影效应影响可以忽略;3×3群桩中阴影效应明显且边桩受到的影响比角桩大。可以用p乘子来定量表示扭转群桩中的阴影效应。在3×3扭转群桩中,角桩和边桩在松砂中的p乘子分别为0.55和0.35,在密砂中分别为0.40和0.35。提出了一个群桩扭转效率系数来评价群桩中不同效应对承载力的综合影响,3×3群桩在松砂和密砂中的效率系数分别为0.71和0.68,主要是受到该群桩中阴影效应的影响。

A series of centrifugal model tests are carded out to investigate the shadowing effect in three-diameter spaced 1× 2, 2× 2 and 3× 3 pile groups under torsion in both loose and dense sands. The test results show that the shadowing effect is significant in 3×3 pile groups, but little, if any, in 1 ×2 and 2×2 pile groups, and such effect varies with group configuration and pile position. The p-multiplier can be used to quantify the effect and values of p-multiplier are suggested. A group efficiency factor is introduced to quantify the general impact of all effects in pile groups under torsion. The efficiency factors of the 3×3 pile groups in the loose and dense sands are 0.71 and 0.68, respectively, in which the shadowing effect plays a dominative role.