Research Of Pile's Dynamic Integrity Test By FEM Simulating

Low strain dynamic test method is the most representative and popular way of pile integrity testing presently. It has been generally accepted for its virtues such as portability, celerity, economy and high veracity. However, this technology still have many shortages. For example, the size of the defects can't be calculated accurately, the influence of the pile material damping can't be identified correctly,and superimposing problems of the deflection waves with many defects in a pile can't be distinguished,Etc. In this paper, the analysis is based on a new FEM software-FEMLAB. Considering the influence of pile material damping and the soil damping, the dynamic response curves of a perfect pile, a pile with many variable defects and a pile in complicated three dimensions are calculated. By comparing the theoretical curves and the actual curves of model piles, the reliability of the software is tested. The influence of the pile material damping is analyzed, which affects the dynamic response curves obviously. The pulse width is wider, the attenuation of the dynamic response is slower. When testing the wave speed, the two peak values need to be selected if the pile material damping is considered. By simulating numerically the dynamic response curves of a perfect pile and adjusting the coupling parameters, the coarse extent of the defect can be gotten. The dynamic response of a perfect pile under complicated three-dimensions is simulated and the variable response curves of variable pile diameters and pile lengths are analyzed. It is verified that test point is put near the half of the radius of a pile. The results of the paper are significant to make clear the influence of variable defects under actual situation.