Ultrasonic is a kind of elastic wave. The concrete medium is regarded as an elastic body. The propagation of ultrasonic waves in concrete obeys the law of elastic wave propagation.
Concrete ultrasonic testing mainly adopts the so-called "penetration method", which uses a transmitting transducer to transmit ultrasonic pulse waves to allow the ultrasonic waves to propagate in the concrete, and then the receiving transducers receive them. Concrete informations, the changes of these parameters can be accurately measured, and concrete properties, internal structure and composition can be inferred.
Ultrasonic testing of foundation piles is to embed the acoustic tube in the foundation pile, place the transmitting transducer and the receiver in the two acoustic tubes respectively, and fill the acoustic tube with water as the coupling medium. When the transmitting transducer emits ultrasonic waves, the ultrasonic waves propagate in the concrete and reach the receiving transducer and are measured and recorded. From this, the concrete sound velocity can be calculated:
(L is the propagation distance of ultrasound in concrete, T is the propagation time of ultrasound in concrete)At the same time, the measurement of the received wave amplitude is to use a certain index to measure the height of the peak of the first received wave, and use them as a relative index to compare the strength of the acoustic signal at each measuring point in parallel.
(A and A0 are the peak value of the first wave and the reference peak value respectively).
When there are defects such as honeycomb, segregation or mud inclusion in a certain section of the pile, the received ultrasonic signal will have the characteristics of reduced wave speed, reduced amplitude, waveform distortion, and change in the main frequency of the received signal. Ultrasonic transmission method of foundation pile detection is to analyze and judge the location and scope of defects based on the relative changes in the measured values of concrete acoustic parameters, and to evaluate the quality of pile foundation concrete.
Ultrasonic is a kind of elastic wave. The concrete medium is regarded as an elastic body. The propagation of ultrasonic waves in concrete obeys the law of elastic wave propagation.
