The geophone tube is the channel through which the probe enters the internal structure of cast-in-place piles during ultrasonic testing. It is an essential part of the ultrasonic testing system for cast-in-place piles. The method of embedding within the pile and the arrangement across the pile's cross-section directly impact the testing results. Therefore, the layout and embedding method of the geophone tube should be indicated on the design drawings, and the quality of embedding should be strictly controlled during construction to ensure smooth testing procedures.

The selection of spiral acoustic probe materials is based on the principle of high transmissivity, ease of installation, and low cost. Sound pulses are emitted from the transmitter transducer, passing through the coupling water to the interface between the water and the acoustic probe tube wall, then through the tube wall to the interface between the tube wall and concrete. After passing through the concrete, they must cross another acoustic probe's two interfaces to reach the receiver transducer.