• The GPR subsystem installs quickly on any rail vehicle and is integrated and synchronized with tie assessment and positional referencing.
• Rail Radar^® data is acquired with a maximum data collection speed of 40kph (25mph) and is post-processed to provide structural and material property parameter measurements at each radar data collection point.

The Rail Radar^® GPR technology:

• Measures variations in material property

Hi-Rail Installed Rail Radar^® GPR System
• The Rail Radar^® System uses a patented high resolution multi-channel surface coupled antenna array based radar system.
• Eliminates the need for destructive test-pitting
• Self-calibrates for layer thickness measurement

The Rail Radar^® GPR system:

Figure 2 Rail Radar^® System Ballast Parameter Calculations
• Single transmit antenna (Tr) and multiple 1.1GHz receive antennas (Rn) positioned at precise locations (sn) to:
• provide accurate structural parameters (dn)
• material property measurements (Vn)
• at each measurement point based on pulse arrival time (tn) for detectable layers in the railbed structure.

The Rail Radar^® system acquires samples at any programmed distance, typically every 25-50mm (1-2 inches), and can typically resolve layers as thin as 40mm (1.5 inches) to a depth greater than 1.5m (5 feet) in normal railbed structures.

• The Rail Radar^® system is able to survey through wooden or reinforced concrete (PCC) ties.
• The Rail Radar^® antenna array has been optimized for rail applications and can be configured to conduct surveys between or outside of the rails as required.
• The Rail Radar^® system has a layer thickness measurement accuracy of ±5%

Ballast Dielectric

Rail Radar^® system has the unique ability to measure non-destructive in-situ ballast assessments for both structural layer thickness and ballast material properties at Hi-Rail track speeds. Using the effects of radar pulse propagation of radar measured ballast dielectric, based on the known aggregate deterioration mechanisms for the transition of ballast from new to fouled conditions under rail traffic loadings.

Ballast Assessment - Field Trials

• Extensive non-destructive testing using the Rail Radar^® system, field ballast samples were carefully referenced and extracted for subsequent laboratory sieve analysis

Field Samples Taken During CN Trials of Non-Fouled and Fouled Ballast Locations
• Rail Radar^® acquired data from 16 separate CN track segments in the Edson Subdivision west of Edmonton, Alberta, Canada

CN Trial Radar Measured Velocity and Ballast Condition Correlation
• Segments included back tracks, sidings, and mainline sections representing ballast conditions ranging from significantly fouled to new ballast

• Radar measured ballast material property variations were correlated to variations in sieve analysis for ballast fouling and ballast moisture content
• Trials confirmed the modeled effects on radar pulse propagation velocity by increased fines associated with ballast fouling
• Trials established conclusively that increased fines (increased ballast fouling) decreases radar pulse velocity
• Trials also demonstrated:
  • that increased fines permit increases in localized moisture content which significantly decrease radar pulse velocity
  • the unique ability of the Rail Radar^® system to measure subsurface material properties (velocity/dielectric) at each measurement point that identifies in-situ variations in ballast material properties

Ballast Quality Index (BQI)

An objective and repeatable Ballast Quality Index (BQI) that is combined wtih gradation testing to accurately quantify ballast fouling.

This objective BQI approach has been theoretically modeled and laboratory and field verified, and can be reported at any interval using client specified statistics.

Simplistically, Rail Radar^® BQI asserts:

• Areas with ballast having higher pulse propagation velocities have more air voids than lower velocity areas for the same ballast material.
• Areas of conventional ballast material having velocities less than 20-30% (25-40mm/ns) of new ballast areas can be considered significantly fouled.
• Areas with ballast velocities exceeding the velocity of acceptable ballast quality areas (acceptable ballast velocity threshold) are indicative areas with fewer fines than acceptable ballast.
• Areas with ballast velocities below the velocity of acceptable ballast quality areas (acceptable ballast velocity threshold) are indicative areas with more fines than acceptable ballast.

Rail Radar^® Ballast Thresholds - Acceptable (Good Ballast) and Fouled (Poor Ballast)

The Rail Radar^® ballast classification process uses sophisticated post-processing techniques that compare actual GPR measured representative ballast material property parameters to client identified thresholds of acceptable and not acceptable ballast conditions.

• Acceptable ballast is defined by the client's fouling specifications for ballast not requiring replacement (recognizing that any increase in fouling would degrade the ballast to requiring replacement).
• Acceptable ballast specification may change based on client criteria such as track classification and maintenance funding levels.
• Typically, it is far easier to identify definitive Good and Poor ballast areas and then determine the corresponding velocity thresholds for an area.

Once these areas are identified, site-specific Good and Poor ballast velocity thresholds are established either through laboratory sieve analysis of field samples or through the analysis of Rail Radar^® measured velocities in these areas

Once Good and Poor ballast velocity thresholds have been established, the Rail Radar^® BQI in relation to these thresholds are assessed and reported

Ballast Condition Overlay Plan Maps

• Rail Radar^® Ballast Overlay Condition plan maps compare measured radar velocity in all detected ballast layers against Acceptable (Good) and Fouled (Poor) ballast velocity thresholds
• These maps have been developed to classify and color code ballast condition for surveyed locations at client specified intervals
• Classifications categorize the condition of the ballast into Fouled (Poor), Acceptable (Good) and Fair (Marginal)
• Reported ballast conditions are integrated with client GIS systems; both linearly and GPS-referenced.

Ballast Undercutting Prioritization

• Green segments depict areas assessed as Acceptable (Good) ballast condition (low ballast undercutting priority)
• Red segments depict areas of poor ballast condition (high ballast undercutting priority), and yellow represents areas of fair ballast condition
• Yellow or 'fair' sections represent ballast in the marginal condition range which may be undercut if sufficient funding is available or if combined with other close proximity higher priority undercutting activities. Ballast gradation analysis could be undertaken in these areas to conclusively determine appropriate rehabilitation timelines and correlate radar measured velocity parameters.