Features of interaction bored pile with the soil base in the presence of structurally unstable soils

Abstract

During the construction of pile foundations, the pile testing process is necessary and mandatory. Therefore, there is a need for a correct assessment of the interaction elements of the "foundation-pile" system with the provision of a reliable and effective design solution.
 If the soil parameters provided in the reports on engineering and geological searching are used without their prior refinement, this leads to a significant discrepancy in the results of numerical modeling of the interaction of piles with the base and data from field tests. In this regard, there is a need to identify the design parameters of the adopted soil model in order to match the modeling results with the results of experimental studies in a wide range of loads.
 The Hardening Soil Model was chosen to describe the interaction behavior of the elements of base-pile system in this study. The nature of the influence of the three modules identified in the above model was investigated: modulus deformation at 50% of the base strength ( ); compressive strain module ( ); strain module at unloading ( ). The influence of the effect of dilatancy of the sand base was also analyzed.
 At the initial stage of loading, the values of the and modules make a significant contribution to its performance. With further increased loads in the soil, significant plastic shear deformations occur, and accordingly, the parameters of soil strength (c, φ) are the leading parameters. Due to the fact that the upper part of the bored pile is located in structurally unstable soils (bulk soil and plastic sandy loam), and the lower part of the pile is located within sandy soil for a significant part of its length, it is also important to take into account the effect of soil dilatancy (ψ).
 It was found that an increase in the unloading module ( ) reduces not only the settlement along the unloading curve, but also along the load curve.
 The results of comparison of full-scale testing of a bored pile and its numerical modeling of interaction with structurally unstable and sandy soils are presented, and the design parameters of the soil environment model are identified in order to match the modeling results with experimental data at the corresponding specified loads.
 The obtained convergence is within 5% in a wide range along the curve of the load on the bored pile.