Analytical method of load-transfer of single pile under expansive soil swelling

The elastic differential equations of load-transfer of single pile either with applied loads on pile-top or only under the soil swelling were established,respectively,based on the theory of pile-soil interaction and the shear-deformation method.The derivation of analytic solution to load-transfer for single pile in expansive soil could hereby be obtained by means of superposition principle under expansive soils swelling.The comparison of two engineering examples was made to prove the credibility of the suggested method.The analyzed results show that this analytic solution can achieve high precision with few parameters required,indicating its' simplicity and practicability in engineering application.The employed method can contribute to determining the greatest tension along pile shaft resulting from expansive soils swelling and provide reliable bases for engineering design.The method can be employed to obtain various distributive curves of axial force,settlements and skin friction along the pile shaft with the changes of active depth,vertical movements of the surface and loads of pile-top.

A simplified approach for settlement calculation of pile groups considering pile-to-pile interaction in layered soils

A simplified approach is presented for the analysis of the settlement of vertically loaded pile groups. In order to simulate the nonlinear pile-to-pile interaction in pile groups, the soils along the piles are assumed to behave as a series of nonlinear springs subjected to the shaft shear stress at the pile/soil interface. Considering the displacement reduction induced by the pile-to-pile interaction, the shear-deformation method is adopted to approximate the displacement field of the layered soils around the piles, and the equivalent stiffness of the springs is obtained. Furthermore, the load-settlement response of pile groups is deduced by modifying the load-transfer functions to account for the pile-to-pile interaction. The settlements of a laboratory pile groups computed by the presented approach are in a good agreement with measured results. The analysis on Contrastive parameters shows that the settlements of pile group decrease with the increase of the pile space and pile length, and the part of piles exceeding the critical pile length has little contribution to the beating capacity of the pile groups.