Undrained lateral behavior of short pile under combination of axial, lateral and moment loading in clayey soils

Pile foundations are often subjected to combinations of vertical, lateral and moment loads. The current design practices assume that the effect of these loads is independent of each other; hence the pile design is carried out separately for vertical and lateral loads. Therefore, in this study, the interaction between axial and bending moment with lateral forces acting on vertical solid concrete pile in undrained clayey soils is investigated by means of numerical modeling. For this purpose the three dimensional (FLAC(3D)) finite difference model was used and the obtained results are compared with Reese's p-y method and Broms' solution. The soil is modeled using the elasto-plastic Mohr-Coulomb constitutive model, and the pile is modeled using linearly elastic beam elements with interface properties. The results show that, in piles under combination of lateral and moment loading, there is an increase in lateral behavior under the presence of vertical loads. Under these conditions, the vertical load has an important role for mobilizing the end bearing capacity and, also, frictional capacity along the pile perimeter due to the adhesion between soil and pile. Therefore, the mobilized shear stresses of soil around the pile are higher in the presence of vertical load as compared to the pure lateral load case. The effect of vertical loads on the percentage improvement in lateral capacity (PILC) seems to be more dominant at lower slenderness ratios. In other words, the influence of vertical loads can be noted to be the highest for short pile.