ELAND PLATINUM Ground Penetrating Radar Xstrata Alloys GROUND

ELAND PLATINUM - Ground Penetrating Radar Xstrata Alloys GROUND PENETRATING RADAR A Basic Overview to RAdio Detection And Ranging 2010 -09 -27 1

ELAND PLATINUM - Ground Penetrating Radar Agenda: HOW GPR WORKS ANATOMY OF A RADAR RECORD GPR DETECTION CAPABILITIES ELECTRICAL PROPERTIES OF MATERIALS GPR PENETRATION DIELECTRIC CONSTANTS OF COMMON MATERIALS REFLECTION STRENGTH GPR DEPTH OF INVESTIGATION GPR APPLICATIONS CONCLUSION 2

ELAND PLATINUM - Ground Penetrating Radar HOW GPR WORKS Theory The unit transmits a short pulse of radio signal, and measure the time it takes for the reflection to return. The distance is one-half the product of the round trip time and the speed of the signal. The receiver does not detect the return while the signal is being transmitted. Through the use of a device called a duplexer, the radar switches between transmitting and receiving at a predetermined rate. minimum range is calculated by measuring the length of the pulse multiplied by the speed of light, A similar effect imposes a maximum range as well These two effects tend to be at odds with each other, and it is not easy to combine both good short range and good long range in a single radar. The Typical System is a low power GPR system that transmits electromagnetic energy in the frequency range of 16 MHz to 2600 MHz (2. 6 GHz) into the subsurface. The total power transmitted is only a few milliwatts; less than that of cellular telephones. 3

ELAND PLATINUM - Ground Penetrating Radar HOW GPR WORKS Practice SIR-3000 console transmits signal via cable to antenna Antenna radiates a cone of energy Energy is reflected off of “interfaces” Antenna receives reflected signal and transmits to console 4

ELAND PLATINUM - Ground Penetrating Radar ANATOMY OF A RADAR RECORD Time/Depth Surface Horizontal axis is the antenna position on the surface Reflection from interface 5

ELAND PLATINUM - Ground Penetrating Radar GPR DETECTION CAPABILITIES • DEPTH OF PENETRATION § Highly dependent on subsurface conductivity (to be discussed later) § Maximum depth: ± 30 meters (this is in ideal soil conditions) § 400 Mhz antenna : ± 4 m (this is the antenna we have to use for hard rock) • SIZE OF OBJECTS DETECTABLE § Smallest in soil: Wire mesh (millimeters) § Largest in soil: Geological features (hundreds of meters) § Smallest in hard rock: Wire mesh (: A few cm) § Largest in hard rock: Geological features (tens of meters) 6

ELAND PLATINUM - Ground Penetrating Radar ELECTRICAL PROPERTIES OF MATERIALS • ELECTRICAL CONDUCTIVITY § Siemens/meter (S/m) § The ability of a material to conduct electric current § The reciprocal is resistivity (high conductivity = low resistivity) § The value is primarily controlled by water content and/or clay content § Higher conductivity makes radar signal penetration difficult § Resistivity < S/m are VERY difficult GPR conditions DIELECTRIC CONSTANT § Dimensionless measure of the capacity of a material to store a charge; § The value ranges from 1 to 81 (AIR = 1, WATER = 81) § The value is primarily controlled by water content; § Dielectric constant differences at boundaries cause reflections in the radar data; § The strength of reflections is controlled by the contrast in the dielectric constants of the two adjacent materials. 7

ELAND PLATINUM - Ground Penetrating Radar GPR PENETRATION depth in feet 300 MHz antenna Electrical conductivityin inmmhos/m terrain conductivity 8

ELAND PLATINUM - Ground Penetrating Radar DIELECTRIC CONSTANTS OF COMMON MATERIALS AIR 1 SNOW PVC 3 ASPHALT FRESHWATER ICE CONCRETE ROCK GRANITE SANDSTONE SHALE LIMESTONE BASALT SOILS AND SEDIMENTS FRESH AND SALTWATER 1 -2 3 -5 4 4 -11 (5) 4 -7 6 5 -15 4 -8 8 -9 4 -30 81 9

ELAND PLATINUM - Ground Penetrating Radar % Water Content EFFECT OF WATER ON DIELECTRIC CONSTANT Dielectric Constant 10

ELAND PLATINUM - Ground Penetrating Radar REFLECTION STRENGTH The strength of a reflection is dependent on the difference in dielectric between the host & the target? Simply put … If the dielectric contrast between the two rocks is too small, you will not reflect enough energy to see the target Reflected waves ` Transmitted waves 11

ELAND PLATINUM - Ground Penetrating Radar GPR DEPTH OF INVESTIGATION • DECREASES AS: Conductivity of the rock increases Water Content Increases (especially if salts are present) Clay Content Increases Scattering Increases (if the feature is not parallel to the hanging wall) GPR user has no control over these factors • INCREASES AS: Antenna Frequency Decreases (but this decreases resolution/sensitivity) GPR user has control over these factors. These factors not only change from day to day but from area to area. The ability to interpret a radar plot is as much an art as a science. 12

ELAND PLATINUM - Ground Penetrating Radar NORMAL INVESTIGATION DEPTHS OF GSSI ANTENNAS Frequency (MHz) Typical applications Depth (m) 16 – 80 Geologic 5 - 30+ 100 Geologic, Environmental 400 Geotechnical, Utility detection, Environmental Archaeology 900 Concrete NDT, Soils, Archaeology, Bridges 0 -1 1500 Concrete NDT 0 -. 5 4 - 25 1 -4 13

ELAND PLATINUM - Ground Penetrating Radar GPR APPLICATIONS • UTILITY DETECTION & NDT § Utilities (pipes, cables), rebar and voids 14

ELAND PLATINUM - Ground Penetrating Radar GPR APPLICATIONS • TRANSPORTATION ENGINEERING § Transportation: roadways and railroad tracks § Ice thickness 15

ELAND PLATINUM - Ground Penetrating Radar GPR APPLICATIONS • ENVIRONMENTAL § Hazardous waste mapping § Storage tank detection 16

ELAND PLATINUM - Ground Penetrating Radar GPR APPLICATIONS • MILITARY § Ordnance detection § Runway integrity • ARCHAEOLOGY 17

ELAND PLATINUM - Ground Penetrating Radar GPR APPLICATIONS • MINING SAFETY § Imaging of hanging wall for fractures & faults § Identification of ramps and sills 18

ELAND PLATINUM - Ground Penetrating Radar CONCLUSION • Radar requires an exposed surface to operate. • Radar detects change in electrical conductivity • Radar is one dimensional. • Many readings and computations are required to return an image (2 D or 3 D) • It takes a skilled operator and a skilled analyst to get meaningful results. • You need to have a good idea of what you are looking for before you start. • With an increase in frequency we get better resolution but worse penetration. • Water and clays absorb the radar pulse and weaken return. • Radar is one of the many powerful new tools available. 19