Assessing the conditions of pavement allows for efficient long-term planning of municipal roads and bridges.
The Financial Accountability Office of Ontario (FAO) estimates that the Current Replacement Value* of municipal infrastructure in Ontario was $484 billion in 2020, with 35 per cent, or almost $171 billion of the total attributed to municipal roads and bridges. According to a recent FAO report, 56.2 per cent of roads and 49.8 per cent of bridges are structurally deficient and in need of repair or renewal, requiring $21.1 billion to eliminate the road deficiency backlog alone. For the last few decades, Ground Penetrating Radar (GPR) has gained popularity as a very effective tool for evaluating subsurface conditions of transportation infrastructure. The analysis of GPR data collected in bridge and road inspections provides valuable insights that allow infrastructure asset managers to effectively plan and budget the rehabilitation and subsequent maintenance of these assets for efficient long-term functionality.
Producing Sound Investment Decisions
New roads and bridges typically enter service in a state of good repair. However, over time these assets deteriorate due to aging and ongoing use. They eventually fail to deliver the acceptable level of the intended service. When that happens, transportation asset managers endeavour to bring the asset back to a state of good repair. While doing so, they are always seeking ways to save money while determining what needs to be repaired or replaced. Their focus is on maximizing the use of the roads and bridges, minimizing related costs, and balancing the needs against other priorities.
GPR Offers Valuable Intel Essential to Transportation Asset Management
Sound transportation asset management relies on the ability to capture and interpret a wide range of infrastructure-related information. This includes asphalt, concrete, and granular thickness; detecting pavement damages, such as cracks and voids; evaluating subsurface moisture conditions of pavement; as well as the structural integrity of bridge rebar and post-tension cables, among others. Traditional inspection methods, when applied on their own, fail to capture a continuous profile of a road or bridge deck. For example, localized sampling, such as coring, may not account for varying degrees of deterioration over a vast area that can worsen over time. Integrating GPR into the evaluation program closes this information gap by capturing subsurface data across these large areas, and reports on anomalies deep below the surface for a fraction of the cost of traditional methods, including the cost of drilling a single borehole.
GPR Applications for Transportation Asset Evaluation
GPR is a non-invasive and non-destructive technology (NDT) that enhances and improves the range and certainty of information that can be obtained in the evaluation and characterization of pavement systems, soils, and environmental problems. The technology works by transmitting high-frequency radio waves into the ground or structure, analyzing the reflected energy to create a profile of the subsurface features. The reflections are caused by a contrast in the electrical properties of subsurface material, which can be indicative of changes in moisture levels, pavement thickness, cracks and voiding, rebar or post-tension cable deterioration, and other factors. The applicable uses of GPR make the technology an ideal tool for new road alignment investigations, highway bridge site investigations, and for road-strengthening projects where construction of a new road alignment alongside an old roadway is required.
GPR Surveys Save Time and Money on Road and Bridge Repairs
Data collected through GPR surveying are invaluable when decisions are made around the prioritization of road or bridge deck rehabilitation and maintenance spending. By taking a proactive approach and integrating GPR surveys into routine operational assessment programs, transportation asset managers can reduce overall lifecycle costs of roads and bridges as well as extend the longevity of the infrastructure’s intended service.
Adding GPR surveys to the condition assessment process serves to improve infrastructure reliability in a few key areas and offers clear cost advantages:
Identifying pavement distress early on
Defects and wearing reduce the structural capacity of a road or bridge over time and can lead to an eventual failure. These defects are often not visible, particularly when a surface has been repaved. Existing pavement layer thickness measurement methods such as core sampling are time-consuming and expensive and only provide information at the test location. GPR surveys can detect areas that are unusually thin or thick and identify subsurface defects below asphalt overlaid roads and structures in real-time and across large distances at posted speeds for a more comprehensive picture of the infrastructure’s condition. This empowers decision-makers to thoroughly and accurately assess the structural adequacy of roads and bridges so that they’re able to identify immediate repair needs and spend limited budgets wisely.
Reducing the need for destructive testing
Core sampling is costly and can create weaknesses in a road or bridge. Incorporating GPR surveys into a structural assessment greatly reduces the amount of drilling required to capture data, and it fills in information gaps between discrete points, allowing project stakeholders to save on costs and minimize traffic disruption.
Recording digital data for future use
Each time a condition survey is completed using GPR, subsurface inspection data can be added to a digital record to be referenced years down the line for future rehabilitation projects. This makes it possible to examine patterns of deterioration over time and evaluate the effectiveness of ongoing maintenance strategies.
Minimizing service disruption
With the cost of traffic congestion estimated at more than $166 billion a year across Ontario, GPR offers the added advantage of capturing data at posted speed limits, often eliminating the need for road closures and traffic control.
Taking a Proactive Approach to Infrastructure Management with GPR Surveys
Maintaining transportation infrastructure in a state of good repair is generally the most cost-effective strategy over an asset’s life cycle but isn’t the only consideration for transportation asset managers with multiple budgetary priorities. Unfortunately, postponing repairs raises the risk of service disruption and increases the costs associated with the municipal infrastructure over time. Sound decision-making and preventative maintenance are key to managing municipal pavement infrastructure costs effectively. That is why incorporating GPR surveys into the routine road and bridge inspection programs is good practice. GPR surveys help maximize the allocation of municipal infrastructure budget dollars, improving planning, increasing the longevity of structures, and reducing lifecycle costs.