engineering investigation of candidate sections for pavement rehabilitation are
sometimes superficial as many of the decisions are based solely upon pavement
rating scores from visual surveys and pavement roughness measurements. While
these serve important functions in defining the condition of the roadway and
providing clues as to the causes of deterioration, there should be a more
thorough investigation to examine subsurface conditions. This will help improve
decisions regarding the scope and design of rehabilitation. However, thorough investigations of
subsurface conditions are often not conducted due to various reasons such as
minimizing exposure of personnel to traffic, lack of personnel to carry out the
testing, expense of data collection and analysis, etc. The means for using
technology to overcome these concerns exist and can be used to characterize
roadway conditions with minimal risks. Some examples of tools and their
applications are discussed below.
weight deflectometer (FWD) has been in use since the 1980s and has proven to be
reliable in assessing the structural condition of pavements. Although rolling
deflectometers have been developed and used in some instances as discussed
below, the FWD continues to be the workhorse in structural evaluation. While it
provides crucial information, the FWD can be made more powerful when it is
combined with information from a ground penetrating radar (GPR).
GPR has been
in general use since the 1990s to investigate pavement issues such as layer
thicknesses, subsurface wet zones, layer delamination, and layer densities
(GFS, 1992; Scullion et al., 1996; Kassem et al., 2016; Dai and Yan, 2014).
Layer thickness information is crucial to the accurate interpretation of FWD data,
as the in-place layer depths and as-built drawings can sometimes differ
substantially. Detection of wet zones in the pavement profile (e.g., between
granular base and asphalt layers) will also help explain areas of high pavement
deflections, and point to the need to improve drainage.
conditions are crucial to the performance of pavements, and while roadways are
originally constructed with systems of well-designed ditches, culverts, and
detention ponds, the surrounding landscape and land use can cause the flow of
groundwater to change over time. Gurganus et al. (2017) have demonstrated the
use of light detection and ranging (LIDAR) equipment for rapidly assessing
roadway drainage characteristics and determining corrections needed in the
design of slopes, ditches, and underdrain systems ahead of rehabilitation
efforts. This information, in addition to the relevant GPR data, can be used to
design improved drainage and mitigate subsurface moisture conditions.
The technologies discussed are all in various states of usage in
the U.S. and serve as examples of how valuable information can be gathered
rapidly and nondestructively for the purposes of pavement rehabilitation
design. Identifying localized distress which may need more extensive repair ahead
of design will allow engineers to more realistically design and plan for the
project rather than discovering hidden conditions at the time of construction.
An example of how these technologies can be used in concert is found in Maser
et al. (2017). A deflectometer moving at highway speed and ground penetrating
radar were used to obtain a combination of pavement layer moduli and
thicknesses to perform a structural analysis of the East Idaho Loop Corridor
(EILC). As a part of this effort, the team correlated the traffic speed
deflectometer (TDS) with the falling weight deflectometer (FWD) measurements
and verified GPR layer thickness measurements with roadway core data. They were
able to divide the roadway into segments based upon the remaining life of the pavement
to improve project planning for future rehabilitation.
Dai, S. and Q. Yan (2014) Pavement Evaluation Using Ground
Penetrating Radar. Proceedings. Geo-Shanghai 2014. American Society of Civil Engineers.
Reston. pp. 222-230.
Geotechnical Society of Finland (GFS) (1992) Ground Penetrating
Gurganus, C., N. Gharaibeh, and T. Scullion (2017) Case Study on
the Use of Mobile Lidar to Produce Preliminary Drainage Design. Transp. Res.
Rec. No. 2655. Transportation Research Board. Washington, DC. pp. 82-90.
Kassem, E., A. Chowdhury, T. Scullion, and E. Masad (2016)
Application of Ground-Penetrating Radar in Measuring the Density of Asphalt
Pavements and Its Relationship to Mechanical Properties. Int’l. Jn. of Pavement
Engineering. Vol. 16, No. 6. Taylor and Francis. pp. 503-516.
Scullion, T., C. Lau, T. Saarenketo (1996) Performance
Specifications of Ground Penetrating Radar. Proceedings. 6th Int’l. Conference
on Ground Penetrating Radar. Sendai, Japan. pp. 341-346.
Saarenketo, T. (2008) Ground Penetrating Radar. Chapter 13. Ground
Penetrating Radar: Theory and Application. Harry M. Jol, ed. Elsevier.
Maser, K., P. Schmalzer, W. Shaw, and A. Carmichael (2017)
Integration of Traffic Speed Deflectometer and Ground Penetrating Radar for
Network-Level Roadway Structure Evaluation. Transp. Res. Rec. No. 2639.
Transportation Research Board. Washington, DC. pp. 55-63.