Abnormal effect of skin friction of bored pile in Shanghai

Based on the tests of bored piles in Shanghai,the relationship between the ratio γ of measured values of skin friction of bored piles to suggested value recommended in foundation design codes of Shanghai was analyzed and the inconformity of skin friction of bored pile to soil properties was divided into positive and negative abnormal effect,which was taken as the appreciation index of construction technique of bored piles.It was shown by the serious negative abnormal effects emerged in deep embedded soils that there was serious defect in natural slurry of normal rotary boring construction method of Shanghai to develop the inherent and potential advantage of good soils embedded deeply,the reasons for which were analyzed according to the action and technology of boring slurry.The positive abnormal effects emerged in shallow embedded soft clay show that some special technology of construction method of bored piles in Shanghai was advantageous to develop skin friction,the reasons for which were analyzed in accordance with special technology of concreting.