Ultrasonic Signal-Transmission Techniques for Compact Microtunneling Systems

Abstract

This paper describes ultrasonic transmission techniques for sensor signals transmitted through water-filled pilot pipes for underground microtunneling systems. Underwater ultrasonic waves are expected to be used for transmitting the orientation and location signals of a remote controlled machine. We have investigated the relationship between ultrasonic transmission loss and frequency for propagation distance in water-filled pipes. Digital signals can be transmitted at 100 bps for more than 50m distance in 80-mm-diameter steel pipes by using underwater ultrasonic pulse waves over 300kHz. A compact prototype ultrasonic transmitter and receiver are developed, making it possible to transmit and receive digital signals by processing their signal waveforms through flowing water in the pilot pipes. Field trials indicate a range of signal transmission of pitching angle over 40-m distance for an actual compact microtunneling system.