Study On Settlement Calculation Of Pile Foundations By Load Transfer Method

Although pile foundations are applied widely, Settlement calculation is one of the difficult problems in the design of pile foundations. The interaction among the piles acts very important in the settlement characteristics of pile groups. The interaction among the piles changes not only the value and development of shaft friction resistance and bottom resistance and the distribution of shaft friction resistance of the single pile in the group but also the stress distribution of soil. The settlement characteristics of pile groups become more complicated than that of a single pile because of the cap-pile-soil interaction. So almost all of the settlement calculation methods of the single pile are not applicable to pile groups.The development and application of pile foundations is summarized firstly. Then, the settlement characteristics of pile groups under axial loading are discussed and all kinds of domestic and overseas methods of settlement calculation are analyzed. The load transfer method is usually used to analyze the load transfer mechanics of the single pile shaft, while it is not applicable to pile groups because it can not consider the soil continuity. The shear deformation method can consider the interaction among piles expediently, so the displacement fields in the surrounding soil of each pile in the group caused by shaft friction resistance are obtained by it. Then, with the new displacement fields obtained by considering the reduction effect caused by the existence of piles and superimposing the displacement fields in the surrounding soil of each pile in the group, the equivalent stiffness coefficients of unit thickness soil around each pile are developed, taking into account the interaction among the piles. The Mindlin solution is used to derive the equivalent stiffness coefficients of the soil under the pile toe. Based on these two kinds of coefficients and the load transfer method, a new method to predict the settlement of pile groups with elevated caps is advised with relevant calculation formula provided as well. Besides the effect of the interaction among piles upon shaft friction resistance and bottom resistance, the contact between caps and soil and the contact stress make the cap-pile-soil interaction more complicated in pile foundations with low caps. So based on the condition of displacement coordination, a method which can consider the effect of the cap sharing the load to predict the settlement of pile groups with low caps is advised. Furthermore, the settlement of piles and pile groups with different parameters are calculated and...