Abstract
In the previous report, the results of a study on the uplift capacity of short piles subjected to various conditions regarding frequency and acceleration of horizontal vibration and pile length of embedment were presented. From these experiments, we concluded that the ultimate uplift capacity of piles subjected to horizontal vibrations (QD) was much smaller than that without any vibration. The decrease in the uplift capacity of piles subjected to horizontal vibration is closely connected with the horizontal displacement of pile's axis.
In this report, we investigated the relationship of the ultimate uplift capacity and average unit friction force for piles with different diameters (D). In addition, this report investigated the coefficient of skin friction (μD) and that of lateral earth pressure (KD) for the case of D=43mm.
In these experiments, the piles whose diameters were 43mm, 66mm or 83mm with the length of embedments being from 20-40cm were set into dry sand placed at either of the two densities: medium or dense. Also, vibration characteristics controlled were two: frequency ranging from 5-20Hz and base accelerations between 50-200cm/s2.
From the results, the following conclusions were drawn: The average unit friction force of piles subjected to horizontal vibration did not increase in proportion to pile diameter because of scale effect. Particularly, in the case in which the pile length of embedment was short, that tendency was remarkable. The reason why the uplift capacity average unit friction force of the piles subjected to horizontal vibration was much smaller than that without any vibration was thought to be due to the fact that the product of μD by KD around the piles greatly decreased due to vibration of the piles.
