Improvement of methods for pile foundations design on settlement

Introduction. The paper describes a new approach for pile foundations design. The system of mechanical impacts is described in a new way for the pile foundation design based on the foundation settlement taking into account the distribution of elastic deformation of the pile material in a soil base. Materials and methods. In contrast to the existing approaches to determining the pile settlement due to elastic deformations of the pile material, all impacts in the form of load from the pile cap, friction forces on the pile lateral surface and the actual reaction at the pile tip are taken into account differentially according to the principle of forces independence. The new design equation is proposed to describe the distribution of friction forces on the lateral surface of the pile. The friction forces in a homogeneous soil of the base are represented as a parabolic distribution function, and not as a linearly increasing one, as established in the standards. Results. As a result, the equation is obtained for a pile settlement design due to the elastic strain of pile material. An example of calculating the pile settlement according to the proposed method and comparing the results with existing methods is given. Negative friction forces from the reaction of the soil under the lower end of the pile increase the value of the elastic deformation of the pile shaft. Conclusions. The refined equation for calculating the elastic component of the pile settlement makes it possible to obtain a lower value of the settlement in comparison with the standard approach by taking into account the influence of friction forces of the soil along the pile lateral surface. The proposed method for pile foundations design based on the settlement can serve as a justification for the reserve of the load-bearing capacity of the pile foundation according to the settlement criterion which will allows obtaining a certain economic effect.