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Road and bridge pile-based acoustic tube often has problems and related operational specifications when burying
Acoustic tubes used in road and bridge pile testing are prone to various issues when buried underground. These problems can significantly affect the accuracy of the test results, leading to potential errors in assessing the integrity of the pile. Here are some common issues and operational guidelines for proper installation:
First, common problems that occur during the burial of acoustic tubes:
1. The bottom of the pile is a high-risk area for defects. If the construction process is not properly executed, the acoustic tube at the base may bend inward, reducing the spacing between tubes. This misalignment causes the transducers to lose parallelism, resulting in abnormal ultrasonic pulse velocity, reduced amplitude, and irregular signal curves.
2. If the acoustic tubes are not securely fastened or if the spacing between fixings is too wide, they may shift or bend due to the pressure of poured concrete. This can change the distance between tubes, affecting the reliability of the test data. In severe cases, it becomes impossible to determine the pile's integrity, forcing the use of alternative methods like core sampling, which can delay construction progress.
3. When the steel casing is too long and the welding quality is poor, air pockets can form inside the tube. This forces the acoustic signals to travel through air instead of water, causing significant signal distortion and impacting the assessment of the pile’s condition.
4. It is commonly assumed that the transducer is centered within the acoustic tube. However, if the tube has a large diameter, the transducer may move freely, increasing the time delay of the coupling water layer. This affects the sound wave propagation time and introduces greater uncertainty into the test results.
Second, key operational specifications for burying acoustic tubes:
1. **Installation depth**: The acoustic tube should be embedded to the bottom of the pile, with the top extending 300–500 mm above the pile surface. All tubes on the same pile should have the same exposed height to ensure consistency.
2. **Sealing requirements**: The bottom of the tube must be sealed with a blind cover or steel plate to prevent grout leakage. After installation, the top should be covered or plugged to avoid foreign objects falling in during concrete pouring, which could block the tube.
3. **Fixing method**: The acoustic tube can be fixed directly to the inner side of the reinforcement cage using spot welding or wire binding. Fixing points should be no more than 2 meters apart, especially at the bottom and joints. For piles without reinforcement cages, a steel bracket can be used. To maintain parallel alignment, triangular steel frames can be spot-welded between the tubes.
4. **Joint specifications**: Care must be taken to prevent twisting of the steel cage when placing it in the hole. The acoustic tube is typically installed along with the steel cage segments. The lower section is fixed to the first part of the cage, while the upper sections are temporarily secured. At each joint, a reverse-threaded sleeve or welded casing can be used. The sleeve should include a soft rubber seal, and the connection should be strong enough to prevent bending or disconnection. The joint must be smooth and free of weld slag or burrs to allow unobstructed movement of the transducer.
5. **Water filling standards**: Each section of the acoustic tube should be filled with clean water as a coupling medium. River water should not be used, especially during flood season, due to high sediment content. Water must be purified before use to prevent blockage at the bottom of the tube. Before pouring concrete, check the water level in the tube and refill if necessary.
6. **Testing procedures**: Pile testing should begin after 14 days of curing. Before testing, the pile head should be chiseled to the design elevation. A 20 cm-long, 32 mm-diameter steel bar can be used to test the smoothness of the tube, and the tube should be filled with clean water for optimal signal transmission.
For more information on acoustic tubes and their proper installation, contact Zhangzhou Lianyu Steel Pipe Co., Ltd.
Phone: 15231769003
Tel: 0317-2012503
Website: http://news.chinawj.com.cn
Editor: Hardware Business Network Information Center
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