INTERACTION OF DRILLED PILES WITH NONLINEAR SOIL BASE

Abstract

The problem of the bearing capacity of soil foundations remains relevant due to the continuous growth of industrial and civil construction and the necessity to design reliable and cost-effective structural systems.

One of the characteristic features of soil behavior is that, when individual soil particles reach the limit state, no significant increase in plastic deformations occurs immediately. The dispersed nature of the soil medium leads to the fact that its current state and properties depend on the previous loading history. The stress state is determined not only by the instantaneous values of deformation but also by the history of the development of these deformations. Therefore, the applied significance of the mathematical theory of plasticity for soil foundations is considerably greater than that of the classical elasticity theory, which is valid only for soils subjected to relatively low stress levels, since approximately 95% of soil deformations are nonlinear. In this study, the application of the numerical Boundary Element Method (BEM) to the solution of a relevant three-dimensional contact problem describing the behavior of a bored pile under loading is considered. The proposed methodology is based on the BEM and a dilatancy-based nonlinear soil deformation model [2,3]. The Ilyushin method, which relies on a linearized system of governing equations, was employed in the analysis. The aim of the study is to determine the stress–strain state of bored piles throughout the entire loading process. This type of pile is among the most widely used foundation elements in geotechnical engineering. The numerical approach is illustrated by calculations of the stress–strain state of the pile at each loading increment, taking into account the dilatancy properties of the soil through the use of an elastoplastic soil foundation model. A comparative analysis of the pile bearing capacity obtained from the proposed numerical approach and the current design code provisions is also presented.