Simulation Analysis Of Admittance Curve Of Piles Considering Soil-pile Interaction

In the foundation pile integrality detecting, the time domain analytical method is usually adopted to analysis process field measured signals. In most cases, due to factors such as test condition, testing technology and so forth, the single time domain analytical method can hardly meet the need of engineering detection. Therefore, in this case, frequency domain analysis is necessary to be introduced as complementarity. The mechanical impedance method is one of the low strain testing methods mainly based on frequency domain analysis. among which the stable mechanical impedance method is the one apply an exciting force of amplitude constancy and frequency variation on the pile, and induce vibration of the pile in a test frequency coverage with a acceptant frequency space in order to obtain the velocity admittance curve of the pile. It has many advantages as follows: 1) it centralizes in single frequency exciting force; 2) it has small probability in harmonic distortion; 3) it is easy to control the frequency bandwidth; 4) the test accuracy is very high. As a result of so many advantages, it is easy to recognize the dynamic characters of the pile, and it has already been widely applied in project.In this paper a simplified pile-soil dynamic model is adopted and we get the velocity admittance curves of sound piles and single detective piles through the function of harmonic response analysis in the ANSYS software. It also analyzes the influence of the clay around the pile and the defect degree on the velocity admittance curve (including fundamental frequency, foundation pile partial fixing coefficient, resonance peak frequency difference and peak valley difference), and it makes comparative analysis on the impact of both damping and stiffness factor of the soil around the piles on the velocity admittance curve.In view of the error use of dynamic stiffness as an important analysis indicator in the detection engineering occurs again and again, this thesis makes single factor analysis of the impact of the pile dimension, surrounding soils, pile elastic modulus, defect and characteristic frequency point f M on foundation pile dynamic stiffness.As the effect of soil around the piles is considered in the calculation model of this paper, the conclusion of this paper directs value in the testing application of stable mechanical impedance method.