Soil-pile interface model for axially loaded single piles

Abstract

On the basis of the observed experimental behavior of axially loaded friction piles driven in soft clays, a soil-pile interface model is proposed using the basic Theological units: springs, dashpots and sliding elements. All the mass of soil affected by the presence of the pile is concentrated in a ring of infinitesimal width. Therefore, all the phenomena regarding the soil-pile stress distribution and displacements will take place in this surface. The proposed Theological model is introduced in a general boundary elements formulation for axially loaded piles. In this formulation, the pile is discretized in a certain number of elements in order to consider a variety of phenomena such as: the deformation of the pile, the increment of radial and axial stresses in the soil mass due to load transfer and the stiffness of the different layers it passes across. Parameters of the rheological model can be obtained from a creep triaxial test and a direct shear test. In case the pile cuts through different layers, it is necessary to compute the parameters for each layer. The proposed model is able to simulate the load-displacement behavior of axially loaded floating piles subject to monotonic as well as cyclic loading. It is also possible to determine the load and displacement at the pile tip and shear stress distribution along the pile shaft. Results of the proposed model have been compared with a very well documented series of pile tests carried out in Mexico City. Tested piles were squared 30 cm on the side and were driven 10 m in a quite homogeneous clay layer. From these comparisons it can be concluded that the model is able to adequately reproduce the most important aspects of the load-displacement behavior of friction piles driven in clay deposits.