The design of a hard rock permittivity and loss sensor to be integrated with borehole radar
Date
2004-03
Authors
Kotze, Beukes
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
The use of ground penetrating radar, and especially borehole radar in underground mines, is becoming
increasingly attractive. This is due to the improvements in the user friendliness of this system. Borehole
radar is able to sense accurately geological faults and structures hidden inside the rock body and this
information is of value to geologists.
In the quest to increase the accuracy of the radar, it was realized that the borehole trajectory and
surrounding rock properties are needed. This thesis discusses a rock permittivity and loss sensor which is
designed to be deployed in cylindrical hard rock boreholes with diameter of about 50 mm. The sensor
consists of electrodes to produce capacitance that is dependant on the rock properties, and electronics to
measure this dependency. The biggest problem foreseen is that the probe will not be in direct contact
with the rock body.
Cylindrical Electrodes were designed using numerical simulations and physical models. Sensitivity and
noise attributes received attention.
Electronic components were used to sense the small capacitance produced by the electrodes. The
resulting signals are slow changing "DC• voltages from which an indication of the needed properties could
be extracted.
The system was integrated and tested in both laboratory and mine conditions. Test-result-b,ased
improvements were introduced and led to satisfactory working of the probe. However, the deployment
method will need attention before this probe can be used in field conditions.
Description
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2004.
Keywords
Ground penetrating radar, Dissertations -- Electronic engineering, Theses -- Electronic engineering