Thickness of the overburden and its soil layers
Different soil materials have different electrical properties and they have a different response to the ground penetrating radar profile. Therefore, it is possible to interpret the depths of the soil layers and the overburden-rock interface from the data. If the radar signal penetrated through the overburden effectively, it is also possible to evaluate the integrity properties (fracturing etc.) of a rock surface.
Groundwater surface level
In groundwater areas, the ground penetrating radar method is an effective method for determining groundwater level. Information can be utilized in groundwater surveys, groundwater intake and construction in groundwater areas.
Measurements on the waters
Measurements can be carried out in waters, excluding marine areas. The shape of the bottom and the depth of the water, as well as the objects lying on the bottom can be detected from the data. Measurement implementation is most effective during winter on the ice deck, but measurement can also be implemented from a boat or a raft.
Investigations on peat
Peat area survey is a traditional ground penetrating radar application. The most commonly the thicknesses of peat layers are defined.
Underground pipes, wiring, wells and underground concrete structures can be located using the ground penetrating radar method. The track of the detected structures and objects are marked by spray color markings. An estimate of the depth of the object is given as well. In larger areas (air fields, squares, roads etc.), surveying can be performed in systematic manner and a map presentation can be made on the results. Locating the items is useful, especially before the machine-assisted digging in the infra-area.
Investigations of concrete structures are carried out with a high-frequency ground penetrating radar antenna. The high frequency GPR signal penetrated the concrete about one meter. The procedure is an efficient way to find out the internal construction of a concrete structure, such as reinforcement, cabling and piping. In addition, it is possible to estimate the condition of the concrete, i.e. the fractured and moisture suffering sections.
Buried objects locating
Examples of such investigation sites are archeological diggings, unexploded ordnance (UXO), forensic investigations, and other underground burial structures. Systematic measurement can effectively cover large areas and the depth, size and shape of found objects can be estimated.
Contaminants change the electrical properties of the soil and therefore ground penetrating radar method can be utilized in the mapping. By systematic GPR measurements and data analysis unnecessary processing of unpolluted soil can be avoided.
The tunnel applications
Shallow fracturing of the rock, cf. Special applications
Rock mass integrity
The ground penetrating radar measurements can also be implemented in tunnels. The geological structures and fractures maximum research depths are in the range from 6 to 8 meters. The average electrical resistivity of the investigated rock mass defines if the GPR method is applicable in the site.
Applications for the mining industry
Quality assurance of base-of-till (BOT) sampling
The ground penetrating radar method can be utilized to measure the thickness of the overburden. Practice can be used to verify that the taken sample is from the desired depth or desired distance from the bedrock. Depending on the characteristics of the overburden, the maximum depth of study varies greatly. The low-frequency GPR antenna is applied. The measurement is implemented either on the foot or the skis, and low impact on the nature is guaranteed.
In the pre-construction investigations the thickness of the overburden, the shape and integrity of the rock surface as well as the level of groundwater can be defined. Measurements can be performed systematically on large areas, whereby the pre-information of the site geology will be refined.
Construction quality control (pools, damns, etc.)
Mining site geo-constructions are often a combination of soils and aggregates as well as various geo-fabrics and plastics. Often, the ground penetrating radar signal passes through the structures and the measurement data can be used to estimate deviation between design and realized structure. Also erroneous structures can be located. If any used layer structure prevents the use of the GPR method, measurements can be implemented along the construction without disturbing actual construction work itself. Construction QA and QC measurements can done on damns and different types of pools, in principle all the geo-structures can be assessed.
Leakage locating (pools, damns, etc.)
Leaking waters change the electrical properties of the structure. Therefore, ground penetrating radar method can be utilized in the locating the leak point in pool, damn or etc.
Geofcon’s special expertise is Excavation Damaged Zone (EDZ) investigations. The ground penetrating radar data analysis based investigation method allows to estimate the excavation induced damage layer on the tunnel surfaces. The method has been developed in cooperation with the Finnish and Swedish spent nuclear fuel disposal operatives since 2008. The method can also be utilized in civilian excavations to optimizing the excavation practice in relation to the resulting damage zone. This can increase workman safety during the tunnel construction, as well as can lead into savings due to lower need of tunnel supporting acts.