A Calculation Method for Depth of Negative Friction Zone of Rigid Pile Composite Foundation

Abstract:

Based on the loadbearing characteristic and the deformation model of rigid pile composite foundation,the calculation formula of the negative friction area on piles considering the interaction of pilesoilcushion is deduced and confirmed through a tested example.Parametric analysis shows that when the pile elastic modulu is over a certain value,the curve of nl0 tends to be stabilized.Thus,it is not necessary to make a high value of pile strength in composite foundation design.Rationally determination of the replacement rate has an important impact on developing the whole bearing capacity of composite foundation.The depth of negative friction zone will reduce when the soil modulus on the side of pile increasing and the reduction trend will become weak with the increasing of load.A comparison of the results of parametric analysis shows that the change of soil modulus on the side of pile has the greatest impact on the depth of negative friction zone,especially when the soil modulus is small,the depth changes up to 23.6%.Thus,in soft soil area where the rigid pile composite foundation treatment methods are adopted,full consideration should be taken that the soil modulu has great impact on the depth of the negative friction zone.