Specification requirements for Sonic Logging Pipes for cast-in-place piles

Before writing specification requirements for Sonic Logging Pipes for cast-in-place piles, let’s see what is Sonic Logging Pipe.

Sonic Logging Pipe is a sonic detection tool, also known as sonic detection pre-buried pipe. It is a channel for the probe to enter the pile body when the pile is ultrasonically tested. It is mainly used to detect the density, strength and other related characteristics of concrete in structures such as bridges and buildings.

Applications of Sonic Logging Pipes

- Detecting concrete quality:

By emitting ultrasonic waves into the concrete and receiving echo signals, the propagation speed and attenuation of sound waves in concrete are analyzed, so as to deduce the quality indicators of concrete such as compressive strength, uniformity and integrity.

Sonic Logging Pipe is an important part of the ultrasonic detection system for cast-in-place piles. It can detect the quality of concrete non-destructively and avoid damage to the structure.

- Monitoring structural safety:

During the construction of structures such as bridges and buildings, sonic logging pipes can be used to monitor the health of the structure and promptly discover potential structural problems such as cracks and voids.

By regularly detecting and analyzing sonic data, the stability and safety of the structure can be evaluated, providing a basis for structural maintenance and reinforcement.

- Other applications:

Sonic logging pipes can also be used for detailed surveys of foundation soil to provide a basis for building stability evaluation.

In pipeline engineering, sonic logging pipes can be used to detect the working status of pipelines, help identify problems and repair them in time.

sonic logging pipes can also be used to measure the frequency, intensity and duration of sound, playing an important role in acoustic research and environmental monitoring.

The specification requirements for the sonic logging pipe of the cast-in-place pile cover multiple aspects from installation and burial to use, aiming to ensure that the sonic logging pipe can work normally and provide accurate and reliable measurement data. The following are specific specification requirements:

- Installation and burial

Burial depth: The burial depth of the sonic logging pipe should be 50mm~150mm above the bottom of the cast-in-place pile, and the lower end of the sonic logging pipe should be closed. The sonic logging pipe should be buried at the bottom of the pile body, and its burial depth should meet the design requirements, generally not less than two-thirds of the pile length.

Upper end height: The upper end of the sonic logging pipe should be 300mm~500mm higher than the top surface of the cast-in-place pile, and the exposed height of the sonic logging pipe of the same pile should be the same.

Quantity and arrangement:

When the pile diameter is less than or equal to 800mm, there shall be no less than 2 sonic logging pipes.

When the pile diameter is greater than 800mm and less than or equal to 1600mm, there shall be no less than 3 sonic logging pipes.

When the pile diameter is greater than 1600mm or the pile diameter is greater than 2.5 meters, there shall be no less than 4 acoustic detection pipes, and they shall be arranged in a symmetrical shape (such as a square) along the outer side of the pile section.

Fixing method: The acoustic detection pipe can be directly fixed on the inner side of the steel cage, and the spacing between the fixing points shall not exceed 2 meters. The bottom end and joint of the acoustic detection pipe must be fixed. Generally, it can be fixed by wire binding, welding, etc. to ensure that it will not shift or deform during the concrete pouring process.

- Connection method

There are many ways to connect the acoustic detection pipe, including clamping, spiral and sleeve types. The connection should be firm and sealed, and no water leakage or slurry leakage should occur. The specific requirements are as follows:

Clamping type: Use special hydraulic clamps to connect, which is simple and fast to operate and has good sealing.

Spiral type: With a sealing rubber ring, it is connected by spiral tightening, and no welding is required on the spot, saving costs.

Sleeve type: Sealed by electric welding, with high tensile strength and torque resistance. If welding connection is adopted, the weld should be full, without slag inclusions and pores, and the welding strength should not be lower than the strength of the parent material.

- Material requirements

The acoustic detection pipe should be made of reliable quality, corrosion-resistant and high-strength materials, such as steel pipes, plastic pipes, etc. The specific requirements are as follows:

Steel pipe: should comply with relevant national standards, and the wall thickness should not be less than 3mm.

Plastic pipe: should have good corrosion resistance and anti-aging properties.

- Size and appearance requirements

Size: The outer diameter, wall thickness and other dimensions of the acoustic detection pipe should meet the design requirements, and the size deviation should be within the allowable range. The allowable deviation range of the outer diameter is ±2.0%, and the allowable deviation range of the wall thickness is ±5%. When the distance between the two flat plates is 75% of the outer diameter of the acoustic detection pipe, the acoustic detection pipe should not have cracks.

Appearance: The acoustic detection pipe should be straight, with a curvature of no more than 5mm/m. Cracks, scars, folds, and layered lap welding defects are not allowed. Scratches, scratches, and longitudinal weld misalignment of pipe sections shall not exceed 0.1mm. The cross-sections at both ends should be perpendicular to its axis, and there should be no external burrs (internal burrs should not exceed 0.5mm), and the ovality should not be greater than the allowable tolerance of the outer diameter. The two ends of the pipe should be sealed, and the insertion end marking line should be clear. The pipe should be unobstructed and free of foreign matter, and the inner diameter should ensure that the detection probe can pass smoothly.

- Precautions when using

The joints of the acoustic detection pipe should match the interface size and material of the equipment being tested, and have good pressure resistance, wear resistance and chemical corrosion resistance.

Before installation, the acoustic detection pipe should be subjected to sealing tests, such as water injection tests, air pressure tests, etc.

During the production and hoisting of the steel cage, care should be taken to protect the acoustic detection pipe to avoid damage such as collision and extrusion.

During the concrete pouring process, the vibrator should be prevented from directly contacting the acoustic detection pipe to prevent the acoustic detection pipe from shifting or rupturing.

Before conducting the acoustic wave transmission method test, the smoothness of the acoustic detection pipe should be checked, and if there is any blockage, it should be cleaned in time.

- Technical Standards

The sonic logging pipe mainly complies with the standard "Thin-walled steel sonic logging pipe for concrete cast-in-place piles and its use requirements" (GB/T31438-2015). This standard stipulates the technical indicators of the sonic logging pipe, such as the size, wall thickness error range, tensile strength, tensile test, flattening test, bending test, hydraulic test, eddy current damage, sealing test, pull-out test, vibration test and torque test.

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