INTERACTION OF THE PILE AND SURROUNDING SOIL DURING VIBRATORY PILE DRIVING

Subject: a computational scheme of the bottom of deep foundation for analyzing vibrations of the “pile-heavy foundation” system is proposed. It is shown that, in this case, accounting for inertial forces of the pile and friction along the lateral surface of the pile leads to a non-periodic (non-harmonic) damped oscillation of the deep foundation. Research objectives: assessment of displacement and resistance along the lateral surface of a pre-fabricated reinforced concrete pile under vibratory immersion; estimation of key factors affecting resistance of the pile in vibratory immersion. Materials and methods: when solving the problem of interaction between the pile and the surrounding soil during vibratory immersion, analytical solutions of the static and dynamic problems using modified rheological models of soils were used. Analytical solutions are obtained using the software package MathCAD. Comparison of the results of analytical calculations with numerical solutions is performed in the PLAXIS 2D geotechnical software package that implements the finite element method. In the numerical solution of the problem of interaction between the pile and the surrounding soil, an elastoplastic model with Mohr-Coulomb hardening was used. Results: when solving the problem of oscillation of the “system”, various contact models are considered for calculations, including elastic, nonlinear and rheological, taking into account time-dependent hardening. Rheological parameters of soils are used, which can be determined on the basis of special laboratory studies. Conclusions: the proposed scheme for interaction between the pile and the surrounding soil during vibratory immersion describes, with sufficient accuracy, the oscillations of a weighty pile on a viscoelastic soil base, taking into account the resistance along the lateral surface and the frictional forces at the pile-soil contact. The performed analytical and numerical analysis of the proposed model showed qualitative agreement. Allowance for friction along the lateral surface of a weighty pile significantly influences the vibration characteristics of a deep foundation.