| With the advantages of simple operation, fast testing and the low cost, low strain reflected wave method is widely used in testing the pile integrity. However, in most cases, low strain reflected wave can only be used in the aspects of testing the pile defects qualitatively, not in the field of analyzing the type and quantity of defects. Based on the ABAQUS/Explicit, in this paper studies on the law of stress wave propagation in the defective piles and the impact defect degree worked on the waveform and analyses the defect degree quantitively.Firstly, in this paper expounds the pile fluctuation theory, which provides the theoretical basis for the finite element model. And the detail description of the modeling process and the factors which should be considered in ABAQUS/Explicit are introduced. In this paper analyses the influence of stiffness damping of the soil around the pile on the waveformSecondly, in this paper establishes the models of uniform cross-section expanded diameter piles, continuous variable cross-section expanded diameter and the outside necking pile, the outside concrete disintegration, summarizes the low how the damping effect, the defect location, the defect size and the defect thickness influence on the waveform, and establishes the function of the defect degree and the ratio between the amplitude of the incident wave and the reflection wave. Meanwhile analyses effect of Young’s Modulus and Poisson’s Ration on the expanded diameter pile waveform.Thirdly, in this paper establishes the model of dual enlarged diameter pile, and analyses the waveforms when the defect spacing is between0～1/4λ、1/4λ～2/4λ、2/4λ～3/4λ、3/4λ～λ. Based on the relationship between the expanding degree and amplitude, in this paper reaches the law between defect spacing and defect degree.Finally, in this paper studies the influence of the outside necking degree of column pile to the bearing capacity, and concludes the fitting equation of outside necking degree and bearing capacity. |
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