Acoustic pipe material selection, two principles: first, sound transmission ratio two, convenient installation and low cost.
Acoustic pulse from the transmitter transducer sends, through the coupling water to reach the water and measurement of pipe wall of the interface, and then through the wall of the tube to the acoustic pipe wall and concrete interface, through the concrete and then through another acoustic pipe two interface to the receiving transducer.
( a ), steel pipe has the advantages of convenient installation, available welding welding in steel skeleton Bob, can replace part of the bar section, and because the steel pipe with large rigidity. Embedded can basically keep the parallel straightness, at present a lot of large diameter bored piles are used as acoustic pipe steel. But steel prices more expensive:
Steel corrugated pipe is a kind of betteracoustic pipe material, it has a thin tube wall, steel and impermeability, pressure resistance, high strength, good flexibility, usually used for prestressed structure in post tensioning method reserved channels: sound test tube. Can be directly attached to a reinforced soil, available in a number of joint corrugated sleeve. As the bellows is very light, so the operation is very convenient, but the installation should pay attention to maintain their axes.
( two), the plastic pipe acoustic impedance rate is low, with a sound test tube having a larger sound transmission rate, usually used in small piles, in a large pile should be cautious when using - because large diameter pile filled with massive concrete, hydration heat of cement not easy divergence: in view of plastic heat expansion coefficient and the disparity of concrete, the concrete is solidified plastic pipe when the temperature drops to produce a radial and longitudinal contraction, it is possible to and from concrete caused by air or water in the acoustic path, and added more intense reflection interface, easy cause of miscarriage of justice.
Acoustic pipe diameter, usually smaller than the large diameter radial transducer can be l0mm, common specifications are50-60mm diameter. Pipe wall thickness on sound transmission and effects is very small, so, in principle, the wall thickness of the tube is not limited, but the savings from the amount of steel angle pipe wall can bear, as long as the concrete lateral pressure, the thinner more province.