Laboratory Model Experimental Study Of Soil Parameters Of Pile-soil Interaction

Pile foundation has been widely applied in tall buildings, railways, highways, bridges, offshore platforms, port wharfs and many other engineering. Due to the presence of soil around the pile, the defect degree of pile can only be qualitatively analyzed, so it is very important to make an objective assessment of the parameters of soil around the pile. Due to the difficulties in mathematics and mechanics, there are few the research literatures of transient response of pile embedded partially in soil. Experimental methods of testing and determining the parameters of pile-side-soil and pile-bottom-soil are proposed by the laboratory model experiments of pile-soil interaction, and the transient response of single-defect-pile embedded partially in soil under semi-sine exciting fore is researched in this paper. The major contents of this research include:Firstly, the reverberation-ray matrix method is applied to study on the transient axial response of integrate pile and single-defect-pile by considering the influence of the damping of pile material and the parameters of pile-side-soil and pile-bottom-soil.Secondly, Huang-he River sand, loess and saline soil are used as pile-bottom-soil, and the pile without soil around it. The parameters of the three types of soil are tested by ignoring the damping of pile. Further more, the effect of pile-bottom-soil on the velocity wave of pile head is analyzed. It is shown that the denser soil is, the greater damping coefficients and stiffness coefficients are, but the stiffness coefficients comparatively increase more. The stiffness coefficients of pile-bottom-soil have great influence on stress wave propagation of pile. It is also shown that laminar numbers and thickness have greater effect on the reflected wave.Thirdly, Huang-he River sand is used as pile-side-soil, and the pile without soil at the bottom of it. The parameters of Huang-he River sand is tested by ignoring the damping of pile. Further more, the effect of pile-side-soil on the velocity wave of pile head is analyzed while the pile is embedded entirely in soil. It is shown that the denser sand is, the greater damping coefficients are, the faster amplitude of reflected wave decays.Fourthly, loess is used as pile-side-soil, and the pile without soil at the bottom of it, and it is separately buried in sixty centimeters, one meter and one meter and fifty centimeters depth. The parameters of the loess are tested by ignoring the damping of pile. Further more, the effect of pile-side-soil on the velocity wave of pile head is analyzed while the pile is embedded partially in soil. It is shown that the denser loess is, the faster trough upgrades with the amplitude of reflected wave decreases at the same time, the greater damping coefficients and stiffness coefficients are, and the amplitude of reflected wave of pile embedded entirely in soil decreases faster than that of pile embedded partially in soil. Fifthly, loess is used as pile-side-soil, and the pile without soil at the bottom of it, and it is separately buried in sixty centimeters, one meter and one meter and fifty centimeters depth. The parameters of the loess are tested by considering the damping of pile. Further more, the effect of damping and buried depth of pile on testing the parameters of soil is analyzed. It is shown that the damping of pile has great influence on fitting stiffness and damping coefficients of loess, and the values of parameters of soil while pile is embedded entirely in soil are closely equal to that while pile is embedded partially in soil, they can use each other.Sixthly, the velocity wave curves at pile head are tested while the single-defect-pile embedded partially in homogeneous soil. Further more, the parameters of defective pile is determined. It is shown that parameters of soil, defect type, defect degree, defect length, defect burying depth, impulse duration and many other factors have effect on velocity wave of pile head.Finally, Main conclusions are drawn and further research and suggestions are proposed.The paper is supported by the Key Project of Education Ministry in 2008 (208150) and the "QingLan" Talent Engineering Fund of Lanzhou Jiaotong University (QL0507A).