Whether you need void locating or detection of reinforced steel and electrical conduits on your construction projects and renovations, look no further for Idaho GPR services than A-Core Concrete Cutting. Read on to learn how a small device can quickly detect what lies beneath the earth and behind thick walls without using harmful X-rays.

Understanding GPR Technology

GPR is short for ground penetrating radar, alternatively called ground probing radar or georadar. It employs geophysical imaging to scan the subsurface by sending radar pulses. In this method, high-frequency radio signals are released into the surface of a material, which reflects it back with varying degrees. The reflected waves are digitally stored and studied, based on two-way travel time and strength of the returned signal, to detect hidden objects and details.

Parts and Workings of a GPR

A typical ground penetrating radar is composed of three parts:

• The control unit houses a computer, a data-storing device and the electronics that trigger the radar pulse. Depending on the model, it is possible to eliminate the need to transfer scan data to another computer for processing.
• The antenna consists of a transmitter and a receiver. The transmitter amplifies the signal received from the control unit and emits it into the target surface. Up to a thousand signals can possibly be sent and received per second by the system.
• The power supply of a ground penetrating radar can operate with a number of external or internal options: rechargeable batteries, the standard 110/220-volt power source and vehicle batteries.

Effects of Dielectrics and Electrical Conductivity

GPR produces scans of the movement of a signal through a surface. The discovery of a multitude of hidden objects by GPR is facilitated by utilizing the differences in material electromagnetic properties, such as electrical conductivity, dielectric permittivity and magnetic permeability. Surfaces with high levels of conductivity attenuate or weaken the signal. A surface with a high dielectric constant value decelerates the energy pulse, preventing it from traveling far.

Once an energy pulse is sent into the surface, some of the energy is reflected back to the antenna and some keeps traveling through the material and attenuates. When a signal travels through materials of varying electrical conductivity and dielectric permittivity, reflection scans are created on the device. If the difference between the respective values of conductivities and dielectric constants of two materials is high, a strong reflection scan will be generated, for example — movement of an energy pulse from wet to dry sands, which possess dielectric constants of 30 and 5 respectively. The movement of the signal through two materials with close dielectric values will generate a faint reflection.

Uses of Antenna Frequency

The electromagnetic energy wave is emitted at a certain frequency. A high-frequency GPR provides scans with a high resolution, making it ideal for finding conduits and rebar in concrete. A low-frequency radar system provides deeper surface penetration, better suited for large targets. GPR provides lowest depth penetration in water and highest in air. Depth penetration for various elements ranks in the following order, low to high: sea water, concrete, asphalt, clay hale, silt, mudstone, wood, fresh water, sand, gravel, limestone, granite, ice and air.

Ranges of Depth Penetration of GPR

The antenna frequency bears a direct correlation to depth penetration and the size of the antenna — the higher the frequency of a transmitter, the shallower its depth penetration into the ground or surface, and the higher its ability to discover small targets and objects. The following figures show that lower frequencies increase the estimated depth of penetration through a variety of natural and man-made structures:

• Bridge decks, roadways, structural concrete: up to 0.3m (1.0 ft) depth penetration for frequencies of 2600 MHz and 1600 MHz for primary and secondary antennas respectively.
• Bridge decks, roadways, structural concrete: up to 0.45m (1.5 ft) depth penetration for frequencies of 2600 MHz and 1600 MHz for primary and secondary antennas respectively.
• Bridge decks, roadways, structural concrete: up to 0.6m (2.0 ft) depth penetration for frequencies of 1000 MHz and 900 MHz for primary and secondary antennas respectively.
• Archeology, concrete, shallow soils: up to 1 m (3 ft) depth penetration for frequencies of 900 MHz and 400 MHz for primary and secondary antennas respectively.
• Archeology, shallow geology, utilities, USTs: up to 4 m (12 ft) depth penetration for frequencies of 400 MHz and 270 MHz for primary and secondary antennas respectively.
• Archeology, environmental, geology, utility: up to 5.5 m (18 ft) depth penetration for frequencies of 270 MHz and 200 MHz for primary and secondary antennas respectively.
• Archeology, environmental, geology, utility: up to 9 m (30 ft) depth penetration for frequencies of 200 MHz and 100 MHz for primary and secondary antennas respectively.
• Geologic profiling: up to 30 m (90 ft) depth penetration for frequencies of 100 MHz for primary antennas and 16-80 MHz for secondary antennas.

Data Storage and Interpretation

Scanned data is stored on the computer and processed using specialized software by a trained operator. Depending on the individual scenario and requirements, a GPR expert can either provide a line-scan to indicate the approximate location of the target or offer a fully mapped surface analysis incorporating scan hyperbolas and precise depth calculations with minimized background noise.

Scope of GPR Applications

Any object that can reflect electromagnetic waves can be detected by GPR — underground voids, buried objects, gravesites, underground pipes, electrical wiring, ordnance and tunnels, to name a few. A-Core services in Idaho for GPR offer usability across many industries, such as commercial buildings, transportation, mining, dams, power plants, nuclear, government, military, airports and residential by penetrating ice, pavements, soil, fresh water and rock. GPR is not dangerous and it has no site restrictions. Here are some of the services offered:

• Private utility locating
• Concrete mapping
• Void detection

Contact A-Core Today

Since its inception in 1974, A-Core Concrete Cutting has worked with small and large clients in many industries, with commitment to its core values of quality, safety, integrity, communication and customer service. For Idaho ground penetrating radar services or any questions about applications, call A-Core at 855-367-3620 to speak to a representative or visit us on the web.

Sources

https://www.geophysical.com/whatisgpr

http://www.clippercontrols.com/pages/Dielectric-Constant-Values.html