EVALUATION OF AN AIRBORNE RESISTIVITY MEASUREMENT SYSTEM (E-PHASE) FOR GRAVEL LOCATION
The scarcity of surficial gravel in certain areas caused the Saskatchewan Department of Highways to investigate geophysical methods that search to greater depths. An airborne resistivity method (E-PHASE) was chosen as the most promising. The E-PHASE system measures the horizontal and vertical electric components of the electrical field generated in earth by the groundwave from a radio transmitter. The ratio of these components is a function of ground resistivity and the depth through which it applies is an inverse function of the radio frequency. In the system used, the frequencies monitored simultaneously were standard broadcast band, low frequency air navigation band, and very low frequency communication band. The airborne data is computer analysed to enable contour plots of apparent resistivity to be made. From these plots, resistivity anomalies are selected for detailed ground- checking. Evaluation of the E-PHASE system was completed in 1971 and first routine survey flying was done in 1973. Two general areas were surveyed, one where granular soils were suspected to exist between till sheets and the other in remote, heavily-treed terrain. An excellent source, conservatively estimated at 1.5 x 10 to the 6th power t of coarse gravel, was found in the first area; several anomalies look promising in the second area but difficult accessibility has hindered groundchecking to data (August 1974). Further development is required to set boundary conditions for economical usage but the 1973 survey has shown positively that E-PHASE can be used to find surficial and buried deposits of granular soils.
Saskatchewan Department of Highways, CanadaMaterials Research Branch
Regina, SK Canada
- CULLEY, R W
- Publication Date: 1974-8
- Features: Appendices; Figures; References; Tables;
- Pagination: 55 p.
- TRT Terms: Aerial surveying; Electrical equipment; Explosives; Frequency (Electromagnetism); Geological surveying; Gravel
- Old TRIS Terms: E-phase resistivity; Resistivity exploration; Subsurface explorations
- Subject Areas: Geotechnology; Highways;
- Accession Number: 00082904
- Record Type: Publication
- Report/Paper Numbers: No. 21 Tech. Rpt.
- Files: TRIS, ATRI
- Created Date: Apr 8 1975 12:00AM