Research On Vertical And Horizontal Vibration Of Single Pile And Pile Groups In Saturated Soil Based On Theory Of Porous Medium

With the advantages of good seismic performance, small settlement, large capacity and broad applicability to complicated geological conditions, pile as an important deep foundation has been widely used in many engineering fields, including offshore platforms, bridges, railways and highways, large-scale plants, high-rise buildings and so on. The carrying capacity of a pile under dynamic load is related to its field performance, which is dependent on the interaction between the pile and surrounding soils. The pile-soil dynamic interaction goes along with the propagation and dissipation of energy in soil, and leads to the vibration of adjacent piles. Therefore, the study on pile-soil dynamic interaction is the key issue for studying the dynamic properties of single pile and pile groups in soil, and the dynamic interaction of pile-soil-structure.The mechanical properties, especial dynamic behaviors of a pile in saturated soil and single-phase soil make a great difference, due to the flow quality of pore water in saturated soil and the difference permeability of the soil and the pile. It is inconsistent with the actual performance of engineering geology for assuming the soil which consists of soil, fluid and gas as single phase medium. The assumption will certainly result in discrepancies when applying the theories of dynamic performances of pile in single phase soil to the pile and piles in saturated soil and the dynamic interaction of the saturated soil-pile-structure.In this study, the soil around the pile is regarded as saturated porous medium, the macro-mechanical properties of saturated soil is described by the theory of porous medium. Appling the Novak plain strain model to saturated soil, the vertical and horizontal dynamic impedance of soil layer is obtained using potential functions, and the vertical and horizontal vibration of single pile in saturated soil are investigated by means of the Novak layer method. The study of dynamic impedance and response of single pile is extended to pile groups in saturated soil. The vertical and horizontal dynamic interaction factors and the effects of main mechanical parameters of pile and soil are investigated. With the principle of superstition based on interaction factor, the vertical and horizontal dynamic response of pile groups in saturated soil is analyzed; the influences of main parameters on dynamic impedance is investigated taking the 3×3 pile group as an example. A new theory for studying the pile-pile dynamic interaction and dynamic impedance of pile groups in saturated soil is proposed. The saturated soil-pile-structure dynamic interaction under harmonic SH wave is also investigated by regarding the superstructure as a beam model and considering the coupling effect of soil-pile-structure. Some theoretical foundation and reference for seismic design of building are provided.