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GPR Pavement Evaluation For Beginners: What It Is And How It Works

gpr pavementThe focus in transportation infrastructure is often placed on traffic engineering, urban development, and transportation planning. This is because substandard road conditions are responsible for up to one-third of all fatalities on American highways.

However, the importance of transportation planning goes beyond the development and design of the road systems. GPR pavement thickness is also a critical part of road construction.

GPR Pavement Evaluation
GPR, or ground penetrating radar, delivers electromagnetic energy pulses into the pavement by using an antenna and survey vehicle. The pulses allow civil engineer services to map the penetration depth of the road in a nondestructive way.

The pulses are reflected back to the survey vehicle’s antenna. This reflected energy is then captured and displayed via an oscilloscope. This display of the reflected pulses tells transportation planning firms about the properties of the pavement including the thickness of the layers.

Reading The Evaluation
The GPR pavement evaluation will either be in grayscale or color. The evaluation provides a representation of the pavement. The pavement layers are displayed on the evaluation as horizontal bands.

Black and white bands mean the reflections are stronger and that there’s a higher dielectric contrast. Gray areas on the evaluation mean the reflections are weaker and there’s a lower dielectric contrast.

Reflections and dielectric contrast are essential to determine because they indicate how thick the layers of the pavement are. The longer it takes for the reflection to arrive from the top and bottom of each layer, the thicker the layer of pavement is.

Calculating The Dielectric Constant
The dielectric constant of the pavement can be calculated by measuring the radar reflection ratio and the radar amplitude incident. The incident amplitude pulse is determined by the reflection of a metal plate. The metal plate is placed on the pavement surface and completely reflects the incident energy.

A similar method can be used to determine the dielectric constant of the base material in the pavement. Because the base dielectric constant can be influenced by base moisture content, the measurement of the dielectric constant can be used to determine the levels of moisture content.

Quality transportation planning is essential for the development of the American road system. For more information on GPR pavement evaluations and roadway design, contact ACI Corporation today.