Wednesday, July 22, 2009

Ground Penetrating Radar

Ground-penetrating radar (GPR) is a very popular non-destructive testing method that is used in industries dealing in geophysics. Although, there are many non destructive and destructive testing methods in this branch geology which includes study of physics of the earth and its atmosphere, including oceanography, seismology, volcanology, and geomagnetism but, Ground-penetrating radar (GPR) is one of the most steadfast non-destructive testing method. In this highly reliable non-destructive testing method radar pulses are used to test the subsurface of rocks soil, ice, fresh water, pavements and structures.

Ground-penetrating radar, a non-destructive testing method in which electromagnetic radiation in the microwave band (UHF/VHF frequencies) of the radio spectrum are used test the subsurface structures. The signals reflected back from the tested subsurface structures help to detect metamorphism, voids, cracks, fractures, splits and fissures in the surface. In this non-destructive testing method, transmitting and receiving antennas are used to record the signals. The transmitting antenna transmits high-frequency radio waves in the form of short pulses which penetrate into the ground or tested subsurface structure. On the other hand, the receiving antenna record the signals reflected from the tested subsurface. The variation in the signals helps in generating results of the non-destructive testing procedure.

Working of non-destructive testing method Ground penetrating radar

The penetration depth of radio waves is inversely proportional to the electrical conductivity of the subsurface structure. If the electric conductivity of the subsurface increases the penetration depth will automatically decrease. The depth range of Ground-penetrating radar is dependent on three things electrical conductivity of the subsurface, frequency of the transmitted centre, and the radiation power. The penetration depth of ice is very high up to several hundred meters. Dry sandy soils or massive dry materials such as granite, limestone, and concrete have average penetration depth in the range of 15 m. In moist and/or clay-laden soils the penetration depth in very low up to few centimetres only.

Applications areas of non-destructive testing method –Ground penetrating radar

There number of application areas where GPR, non-destructive testing method is widely used, such as:

• Earth sciences like geography, geology, or meteorology to study bedrock, soils, groundwater, and ice.
• Engineering applications like civil engineering for non-destructive testing of structures and pavements.
• Environmental remediation for identify landfills, contaminant plumes and other related sites.
• Archaeology for mapping archaeological features, such as graves, buildings, tools, pottery or other remaining material evidence.
• Military for the detection of mines, unexploded ordnance, and tunnels.

Contact www.abcndt.com, for ground penetrating radar of concrete structures. They use minimum equipment yet deliver instant, radiation free results.

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