Successive approximation graphical method for negative skin friction in piles taking the working load into account

A study on problem of negative skin friction has always been hot in China and abroad. Occurrence mechanism of negative skin frictions is simply analyzed. It is pointed out that both soil sedimentation surround the piles and the working load on the pile top are the main factors that effect the negative skin friction behaviors. The deficiencies in calculation method for negative skin friction in Technical Code for Building Pile Foundations in China are analyzed. The unreasonable factors in Fellenius' method are analyzed, such as pile-soil interaction in the development process of negative skin friction is not taken into account. Based on the above analysis, combining with load-settlement curve of pile obtained by static check-measuring tests, the successive approximation graphical method for negative skin friction calculation is put forward on the premise of pile settlement control. The successive approximation graphical method take the pile-soil interaction during the occurrence, development and stabilization of negative skin friction in pile induced by both soil sedimentations surround the piles and the working load on the pile top. Some actual examples illustrate the application of the successive approximation graphical method. Results show this method is more reasonable and practical.