Theoretical Analysis And Test Research On Saturated Soil-Pile-Structure Dynamic Interaction

A large number theoretical analyses and engineering practices indicate that dynamic soil-structure interaction has a significant effect on the dynamic characteristics of superstructures on soft soil, and the seismic response of which may greatly change. In the past researches on dynamic soil-structure interaction, most researchers took soil as a single-phase viscoelastic continuous medium model. In fact, soil is a tri-phase composite matter, and the saturated soil is a diphase medium which consists of soil particle and pore water. It more conforms to reality to adopt the multiphase model for soil, so, the dynamic soil-structure interaction problem based on the multiphase model has been paid more attentions in recent years. The thesis studies the saturated soil-foundation-superstructure interaction, the focuses of which are on the analytical solutions of vertical, torsional, horizontal vibration impedance of pile. Through the theoretical analysis and the test research, this study tries to understand the dynamic interaction mechanism of soil-foundation-superstructure more profoundly, to provide the guidance for engineering application, and to offer some theoretical bases and design suggestion for the seismic design of dynamic saturated soil-pile-superstructure interaction. The thesis is divided into seven chapters as follows:1. With the summarization of lots of interrelated references, the state-of-the-art of soil-structure interaction is reviewed and the analytical methods for dynamic soil-pile-superstructure interaction are summarized. The limitations, advantages and disadvantages existing in present researches are discussed.2. Base on dynamic consolidation equation of saturated soil preented by Biot, considering the influence of the saturated soil skeleton's radial motion and soil-pile coupling condition, vertical vibration dynamic response of an end bearing pile embedded in the saturated soil is studied rigorously. It is the first time to obtain the vertical dynamic response function of pile neither imported potential function nor applied integral transform. In addition, a simplified solution by introducing the Novak layer method to the pile's vertical vibration impedance research in the saturated soil is derived.3. The soil's formal solution of torsional vibration displacement can be obtained based on equation of dynamic equilibrium of soil at first. Then Related the solution of the equation of dynamic equilibrium of pile and the soil-pile coupling condition, the displacement and velocity response function at pile head in frequency domain are obtained in a closed form. Also, the Novak layer method is introduced to the torsional vibration impedance research of the pile in saturated soil. Few reseach reports on these aspects have been found.4. The horizontal vibration response of the pile in saturated soil is studied according to the direct solution method and potential function method respectively, and the horizontal, rocking and horizontal-rocking coupling impedance are obtained. The Novak layer method is introduced to the horizontal vibration impedance research of the pile in saturated soil. The reports on these aspects have not been found up to now.5. Because of the difficulty of tests, few tests are reported in researches of dynamic soil-pile interation. There are not sufficient test spports to the theoretical analyses,so the application of theoretical results are limited in engineering pratice. In order to strengthen the test research, a 1:2 model test of dynamic soil-pile-frame structure interaction is researched, which is the other main work in this thesis. Under harmonic and impulsive excitation at top of the model and blasting vibration under the floor, lots of test data are got. These data will be benefit to identify the dynamic interaction mechanism of soil-foundation -superstructure and approve the theory of dynamic soil-pile-superstructure.6. A simplified formula that can be used widely is developed to calculate fundamental period of interaction systems. The comparison between test data demonstrates its precision.