Research On Pile Detection And Signal Processing Based On Ultrasonic Method

With the rapid development of China’s infrastructure,piles are widely used in various large-scale construction projects because of their high bearing capacity,wide applicability and strong seismic resistance.However,in the process of pile construction,there are many factors that cause defects such as cavity,horizontal gap and mud inclusion,which damage the integrity of the pile,and may lead to engineering accidents,casualties and property losses.Therefore,it is necessary to effectively detect the integrity of foundation piles,so as to carry out engineering treatment,ensure the quality of construction engineering,and prevent engineering accidents caused by the defects of foundation piles.Compared with other pile detection methods,pile ultrasonic detection method can detect the pile comprehensively,carefully and accurately.In this paper,the ultrasonic testing method of foundation pile is deeply studied:(1)According to the basic theory of pile ultrasonic testing,the finite element complete model and defect model of pile are established in COMSOL multiphysics software by finite element numerical method.The propagation law of ultrasonic wave in pile is analyzed,and the influence of defect size and location on the amplitude and acoustic time of head wave in ultrasonic signal is studied.(2)The hardware circuit for ultrasonic testing of pile foundation is designed.Through the circuit,the ultrasonic signal is excited,limited,amplified,filtered and collected.(3)Aiming at the noise problem of pile signal,based on wavelet threshold denoising and empirical mode de-noising,an EMD wavelet de-noising algorithm based on pile ultrasonic signal is proposed to de-noising pile ultrasonic signal.The signal-tonoise ratio and mean square error are used to evaluate the de-noising algorithm,and compared with the current algorithm.(4)According to the finite element simulation model of defective pile,the defect experimental pile is built,and the typical cavity defect is set.Through the linear change of the relative position between the detection point and the cavity defect,the influence of the defect position on the acoustic time and the amplitude of the first wave in the ultrasonic signal of the pile is studied.In this paper,based on the research of pile ultrasonic testing,through the comparison between the finite element simulation model and the experimental pile,it is concluded that the position change of pile defects will lead to obvious changes in the amplitude of the first wave of the ultrasonic signal,and the closer to the signal transmitting or receiving point,the more dramatic the change of the amplitude of the first wave.In view of the noise problem,the EMD wavelet denoising algorithm proposed in this paper can effectively remove the noise in the pile ultrasonic signal,and the denoising effect is better than the current algorithm.The ultrasonic signal after denoising has high signal-to-noise ratio and small mean square error,which can meet the requirements of pile integrity evaluation by ultrasonic signal,and provide help for further improving the detection accuracy of pile integrity.