Dynamic response of a large-diameter pile with variable section in layered saturated soil considering construction disturbance effect

ABSTRACT

An analytical solution is developed in this paper to investigate the vertical time-harmonic response of a large-diameter variable-section pile, and it considers the radial inhomogeneity of the surrounding soil caused by construction disturbance. First, the saturated soil surrounding the pile is described by Biot’s poroelastic theory and a series of infinitesimally thin independent layers along the shaft of the pile, and the pile is represented by a variable-section Rayleigh–Love rod. Then, the dynamic equilibrium equations of the soil and pile are solved to obtain an analytical solution for the impedance function at the pile top using the complex stiffness transfer method and impedance function transfer method. Finally, the proposed solution is compared with previous solutions to verify its reliability, and a parameter study is conducted to provide insights into the sensitivity of the vertical dynamic impedance of the pile and velocity response in low-strain integrity testing on defective piles.     

Longitudinal dynamic impedance of a static drill rooted nodular pile embedded in layered soil

The static drill rooted nodular (SDRN) pile is a new type of precast pipe pile with equally spaced nodes distributed along the shaft and wrapped by the surrounding cemented soil. In this paper, the longitudinal dynamic response of the SDRN pile embedded in layered soil is investigated with respect to the complexity of the pile body structure and the pile–soil contact condition. First, the shear complex stiffness transfer model is used to simulate the radial inhomogeneity of the surrounding soil. Then, the governing Equations of the pile–soil system subjected to longitudinal dynamic loading are established. The analytical solution for the dynamic response at the pile head is obtained by the shear complex stiffness transfer method and the impedance function transfer method. The degenerate case of the present solution is compared with the published solution to verify its reliability, and the complex impedance of the SDRN pile is compared with that of the precast pipe pile and the bored pile. Finally, a parametric study is conducted to investigate the influence of pile–soil parameters on the complex impedance at the pile head within the low frequency range concerned in the design of the dynamic foundation.     

Assessment of cyclic response to suction caisson in clay using a three-dimensional displacement approach

An investigation was made to present analytical solutions of cyclic response to suction caisson subjected to inclined cyclic loadings in clay using a three-dimensional displacement approach. A model representing the relationship between vertical load and vertical displacement and that between lateral load and lateral displacement along the skirt of suction caisson subjected to cyclic loadings is proposed for overconsolidated clay. For the effect of vertical load on cyclic load capacity of suction caisson, using the Mindlin solution in the case of a vertical point load, the vertical stress of soil under the base of suction caisson is presented. For the stress state of soil beneath the base of suction caisson subjected to cyclic loading, the Mohr–Coulomb failure line and critical state line are presented and the relationship between total stress, effective mean principal stress, stress difference, and pore-pressure is elucidated. The comparison of results predicted by the present method for a suction caisson subjected to cyclic loadings in clay has shown good agreement with those obtained from field tests. Cyclic behavior of clay up to failure is made clear from the relationship between cyclic tensile load, vertical and lateral displacements, and rotation and that between depth, vertical, and lateral pressures.