A Study On Dynamic Characteristics Of Pile In Layered Soils

The defects of pile will necessarily bring negative function to the capacity of the pile, the severe ones will make the pile lost bearing capacity, which does harm to the superstructure. So it can prevent the occurrence of various engineering accident to judge the location and degree of defect accuratly, which is meaningful for engineering. Much work about integrity testing of pile have been done in this article:Firstly, velocity, displacement and acceleration response model of top of complete pile is deduced. Matlab program is worked out from the velocity response model, based on the program, it have acquired velocity response curves effective disciplinarian, which relate to these factors, such as the diameter and the length of pile, the velocity of elastic wave and the stiffness of soil of pile bottom. The disciplinarian can provide basis and referience for the work of integrity judging.Secondly,since one of the main characters of soil stratum is layered property, begain with the wave-damping equation, this paper deduced the solution of Longitudinal vibration of pile,by inverse Fourier transform a semi-analytical solution of the velocity response under semi-shine impulse exciting is obtained. Matlab program is worked out from the semi-analytical solution of the velocity response, influence of the change of aspect ratio , the shear modulus of soil around the pile and pulse width on vibration characteristic of pile is recearched.Thirdly, since the main objective of performing dynamic pile testing is to evaluate the integrity of drill sharfs definitively, this paper deduced dynamic response of the top of varying cross-section pile; then Matlab program is worked out from the dynamic response,It studied the influence on the vibration properties caused by the degree ,the location and the length of pile defects; it drawed the vibration response curve of pile of varying cross-section in foundation pile,then it drawed the conclusion that we would be interfered by the foundation pile when we judged the integrity testing of pile.Finaly, according to the longitudinal vibration model that experiences a resistance from pile side soil and pile end soil, this paper deduced functional relation between the position of the defects,relative stiffness and natural frequency; through numerical simulation of the model, the first three natural frequencies of integrated pile and dynamic pile was obtained , and then recognition diagram, it verified the feasibility of the method.