Using the ultrasonic pulse-echo method for detecting pile quality is convenient, fast, and highly accurate. However, during actual construction, it is difficult to maintain parallelism between the acoustic wave pipes, resulting in measured acoustic time and amplitude values often being affected by the bending and skewing of the pipes. If this effect is not corrected, directly using the detection data to search for defect points may greatly interfere with the test results.

One, the detection method of the ultrasonic transmission method

After the pile borehole is completed and before the concrete is poured, several acoustic wave pipes are parallelly pre-buried into the pile as channels for acoustic wave emission and reception transducers. Using an acoustic wave monitor, the acoustic parameters of the waves passing through each section of the pile along its longitudinal axis are detected at certain intervals, thereby determining any defects in the pile concrete.

What causes the acoustic pipe to be out of alignment?

Due to issues in design and construction, the triangular or quadrilateral sections of the steel cage used to secure the sound measurement pipes are unequal and not parallel. This results in the sound measurement pipes not being parallel after being fixed to the corresponding top points of the steel cage.

During the hoisting and welding of the reinforcing cage, the acoustic measurement pipe was not aligned, resulting in the pipe's deviation during the connection process.

Drilling and bending create lateral pressure on the steel cage at the inner bend, causing it to inwardly凹陷 and move or bend the acoustic measurement tube on that side, thereby losing its parallel alignment.

Section 3: The Dangers of Non-Parallel Sound Detection Pipes

During construction, the acoustic probe tubes often become crooked and bent. If this issue is not corrected and the detection data is used directly to search for defect points, it may lead to light, heavy, missed, or incorrect judgment of defects.

Section IV: Testing and Calibration Methods - Abnormal Characteristics Caused by Non-Parallel Sound Testing Pipes and Their Determination Criteria

1. Anomalous characteristics of sound velocity-depth and amplitude-depth curves caused by circumferential displacement of acoustic survey tubes: Circumferential displacement refers to the deviation of a single acoustic survey tube from the circular arrangement of three or four tubes in a pile. This shortens the distance between a pair of survey tubes, resulting in increased sound velocity and amplitude. Conversely, the distance between the other pair of tubes increases, leading to decreased sound velocity and amplitude. Therefore, by analyzing the complementary relationship between the sound time and amplitude anomalies of the two pairs of detection tubes, it is possible to determine which tube has displaced and in which direction.

2. Abnormal characteristics of sound velocity, depth, amplitude, and depth curves caused by the radial displacement of the acoustic tube: The radial displacement of the acoustic tube refers to one or more acoustic tubes moving closer to or away from the pile center, which leads to an increase or decrease in the sound velocity, amplitude, or both for two or more pairs of acoustic tubes.