Ground Penetrating Radar

Ground penetrating Radar (GPR) is a method used to rapidly survey the depth to bedrock along selected transects, such as along water pipes, planned roads, prospective mines and can be used to locate buried or lost objects. The GPR’s transmitting antenna radiates short pulses of high-frequency radio waves into the ground. These waves are reflected when they hit a buried object or encounter an area with a change in dialectric constants and are converted into a digital picture. If multiple lines are collected systematically over an area, a planview map can be composed.

Refraction Seisomology

Refraction Seismology (RS) is a method for mapping geologic structure by measuring the arrival time of head waves as a function of source-receiver distance. It is commonly used in building tunnels, identifying crush zones and fissures in bedrock or where the depth to bedrock is too great for GPR to be used. Refraction seismology uses a sound pulse (in the form of a dynamite explosion) and a line of geophones extending along a transect. Some of the energy of the explosion that is refracted into the different rock or soil layers returns to the surface to be detected by the geophones.

Geoelectric, electromagnetic and magnetic measurements.

By taking advantage of the fact that ions in soil and groundwater conduct electricity, and that contaminated groundwater often has a high ionic content, the geoelectric measurement of the electrical resistivity of a site can allow, for example, contaminant plumes to be surveyed. Electromagnetic measurements can be used to locate crush zones in bedrock, since crush zones contain water and are often better electrical conductors than the surrounding bedrock. Transmitters on the surface emit electromagnetic currents into the ground, while receivers measure the changes in the current caused by differences in the underground material.

Magnetometers can be used to detect varying levels of magnetite found in different rock layers. Because the level of magnetite is often lower in crush zones than in the surrounding bedrock, magnetic measurements are sometimes used to identify suitable locations for abstraction wells or for measuring the depth to bedrock in tunnel construction projects.