Abstract: A series of centrifugal model tests are carried 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. 更多