Finite Numerical Simulation Analysis Of Reflected Wave Method To Testing In Pile With Defects

Low strain reflected wave method is a widely used method for integrity testing of pile foundation.The theoretical foundation is a wave theory of simplified one-dimensional elastic rod. The field test of defects often only for simple types of discrimination, but the different degree of defect of stress wave reflection is law knowledge, for more accurate identificatting different types extent of defect. In this paper applying finite element analysis software of ABAQUS/Expilcit to establish the hammer-pile-soil system model, through the numerical calculation of the pile for integrity and the pile for defect degree and different types, get the velocity of stress wave signal and the corresponding rules of analysis, By contrast with actual data validation, get to the actual engineering detection has important guiding significance to the related conclusion, the main research contents and results include the following.According to the improved model consider damping effect of pile side soil, get the fixed solution problem under the vibration action in pile top in homogeneous soil of Integrity of pile, drawn instantaneous response solution of the pile top by using the method of separation of variables, further analysis of dynamic response characteristic and reflection and transmission characteristics of stress wave.Applying the finite element analysis software of ABAQUS/Expilcit to establish the model of pile-soil system, combined with the engineering practice through the loading area with a force amplitude load method to match the appropriate source, put attentions and basic hypothesis for forward finite element preprocessing, and applying the method of peak to peak" to calculate the velocity for the pile, Through the integrity of pile obtained by the numerical calculation results and experimental results verified the reliability of the finite element model for the simulation analysis, Simulation analysis for defects of pile foundation.Through the calculation of pile soil model vibration frequency gets stiffness damping coefficient and mass damping coefficient of pile side soil. Analysis of stress wave propagation regularity with the pile soil modulus and damping coefficient of soil. The stress wave propagation characteristics for further research and analysis, Provide some interpretation according to the practical engineering detection.Focusing on the inner side and the outer side of the concrete shrinkage, concrete disintegration, concrete expanding and other different types of defects of the simulation analysis, which focuses on the inner side and the outer side of the concrete shrinkage and disintegration area accounts for the pile section of different proportion and different defect thickness are simulated and analyzed, based on the ratio for incident wave amplitude of pile top and the reflected wave amplitude of defect analysis, we have different degrees of defects on waveform influence rule, obtained the fitting equations between the ratio(A0/A,) various kinds of defects of pile top incident wave and reflected wave amplitude and defect area occupied cross-sectional area, effect of the pile side soil damping in the homogeneous soil, puts some reference for the actual engineering test. To solve the two major problems in field test: defects of accurate qualitative and rapid quantification has important value.