Underground cavity detection by electromagnetic shock waves

摘要

A method for detection of underground anomalies including in a system of distributed antennas (10), which are leaky transmission lines, disposed in 16 boreholes (12) formed in a ground, a transmitter (14) being connected to one of the antennas (10), and a receiver (16) being connected to another of the antennas (10), injecting an electromagnetic pulse into one of the antennas (10), wherein the pulse gradually leaks out, and wherein if a speed of propagation in the line in which the pulse is injected is faster than a speed of propagation in the ground, a shock wave is transmitted through the ground, called a transmitted signal, and received as a received signal at another of the antennas (10), and wherein an underground anomaly diffracts the shock wave, resulting in a detectable disturbance in the received signal, and locating the anomaly as a function of a time delay of the disturbance relative to the transmitted signal.

主权项

1. A method for detection of underground anomalies comprising:
placing an electromagnetic wave transmitter connected to an antenna in a first borehole in a ground; placing an electromagnetic wave receiver connected to an antenna in a second borehole, both antennas for the transmitter and the receiver comprising leaky transmission lines; selecting dielectric and magnetic constants of said leaky transmission lines to be smaller than those of the ground so that a speed of electromagnetic wave propagation through said leaky transmission lines is faster than a speed of propagation through the ground; injecting an electromagnetic pulse into one of the antennas, wherein the pulse gradually leaks out as a shock wave which is received as a received signal at another of the antennas, and wherein an underground anomaly diffracts the shock wave, resulting in a detectable disturbance in the received signal; and locating said anomaly as a function of a time delay of the disturbance relative to the transmitted signal.