Application Research Of Elastic Wave Nondestructive Testing Technology For Pile Foundation Of Nansha Port Railway In Guangzhou

Elastic wave nondestructive testing,as a common method for testing the integrity of foundation pile,is widely used in most engineering tests.It is based on the simplified one-dimensional linear elastic bar wave equation and the change of waveform shown by the change of wave impedance as the criterion.Before the actual detection,operators will build a large number of defect pile models and interpret and study them based on the results of numerical simulation.For now,most of the previous discussion of its numerical simulation is often confined to the simplified model of pile soil "" or " hammer-pile-soil " model,namely the pile soil and pile end soil respectively two kinds of different materials,simulation of hammer excitation load,even to make nylon hammer model,using ABAQUS/Explicit,ANSYS/LS-DYNA,FLAC3 D,PIT-s or COMSOL Multiphysics numerical simulation software to simulate,The results are processed by pre-processing of jiajia software,MATLAB,Surfer 13 and other software and drawn into a graph.The selection model of ABAQUS/Explicit numerical simulation is strictly followed by the engineering geological conditions of no.1 bridge pier and the size and parameters of its foundation pile,and the rationality of the sampling interval during the actual detection process is discussed with the path selection and output frequency selection as the reference objects.The accuracy of the data at different output time points is discussed,and then extended to the actual detection.Suggestions are made on the rationality of setting the sampling interval of the equipment.The influence of the complexity of geological conditions on the curve is discussed in the paper.Taking the diameter of the defect part of the reduced diameter pile as the variable,and the fracture part of the fractured pile as the variable,the possibility reason that the simulated curve could not completely fit the actual detection situation was analyzed and inferred.Secondly,taking a foundation pile of no.1 pier of nansha port railway as the object of discussion,elastic wave detection and acoustic wave transmission detection were performed on it at the same time,and then the advantages and disadvantages of the two methods were discussed.Finally,on the premise of the whole bridge layout plan of no.2 ~ no.8 pier and the geological column chart of the construction borehole,after selecting the appropriate detection method,the detection result is interpreted and the defect determination diagram is drawn.Finally summarizes the elastic wave reflection method is quick,simple,intuitive,without being limited by the space,thus widely used in most of the measured,but is often constrained by measured pile,pile length and pile diameter for elastic wave propagation in pile body happens when the energy attenuation,makes the received signal is relatively weak,makes judging its defect is difficult,so choose to use ultrasonic transmission testing to confirm.Although the acoustic transmission method has high detection accuracy and is more intuitive in data processing to reflect the defect segment and is not limited by the size of foundation pile,it has a high cost,so it is often used as an auxiliary means in actual detection.