Numerical simulation of interaction bored pile and soil mass with taking into account the dilatancy of the soil

Abstract

Pile testing is a necessary and mandatory process of construction buildings and structures erected on pile foundations. There is a need for a correct assessment of the interaction of the elements of the "foundation-pile" system for the reliable and effective design of pile foundations.
 The use of soil parameters provided in reports on engineering and geological investigations, without their clarification, leads to a significant discrepancy in the results of numerical modeling of the interaction of piles with the foundation and data from real observations of their settlement as a result of loads. Therefore, there is a need to identify the calculated parameters of the adopted soil model in order to match the simulation results with the results of experimental studies in a wide range of loads.
 In this paper, a model of ideal elastic-plastic behavior of the soil environment using the Mohr-Coulomb strength criterion was chosen to describe the interaction behavior of the elements of the "foundation-pile" system. When using this model, it is necessary to take into account a number of its inherent shortcomings, for example, not taking into account the change of the young`s modulus depending the change of the stress-strain state. Additionally, this work examines the influence of the dilatancy effect of sandy soil.
 At the initial stage of loads up to 15% of the total settlement of the pile (displacement resulting from potential pile failure), the value of the young`s modulus (E) makes a significant contribution to its operation. At the later stages of loading, significant plastic shear deformations occur in the soil, and accordingly, the leading parameters are the soil strength parameters, in this case, the specific cohesion (c) and the friction angle(φ). Since in this work the drill pile passes through sandy soil for a considerable length, it is also important to take into account the effect of soil dilatation(ψ).
 The results of a comparison field test of the bored pile with large-diameter and their numerical simulation of interaction with sandy soils are presented, and the calculation parameters of the soil environment model are identified in order to match the simulation results with experimental data at the corresponding specified loads.
 A convergence of up to 5% was achieved in a wide range of loads on the bored pile.