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Establishing Applicability of NDT Methods for Project-Level Evaluation

Status: In development


Despite the accelerated development of an array of nondestructive testing (NDT) devices in the last four decades, their use in a meaningful way in the design stage has only recently been implemented by a few DOTs. Significant effort has been focused on ensuring the devices are calibrated and functioning properly. Given that each device has certain limitations and is applicable under specific conditions, the proper use of the collected data with these NDT devices in the day-to-day design has been ambiguous.

Two examples of well-known NDT devices are GPR and FWD. Some of their advantages and limitations can be summarized in the following manner.

  • The versatility of GPR in providing useful design information in terms of layer thickness and establishing saturated zones in subgrade is well documented. However, there are many cases where the usefulness of GPR is limited (e.g., the presence of water or steel, the similarity of dielectric constants between adjacent layers, etc.). What are the extent and limits of dielectric properties that can be utilized to detect problem areas within pavement?
  • The reproducibility and speed of collection of FWD deflection data are excellent. However, the backcalculation process is nonunique, especially in the absence of as-built layer thickness information and for complex multilayer systems. Recent work related to the calibration of multilayer pavement response models with actual field data has clearly shown that without careful backcalculation, the predicted critical strains within different pavements will be significantly wrong. One way of using FWD data more practically and pragmatically is to use indices. How much contrast in properties and to what extent the contrast should exist for providing adequately accurate information to the designer?

This list can be expanded for a number of other well-known and up-and-coming technologies.

Based on the background above, the goal of this project is to establish the usefulness and the probability of successful detection of defects by traditional and new NDT methods as a pre-design survey tool. In that manner, the design engineers will know which NDT device to deploy when and how to use the data to improve their design.

Project Tasks

Task 1: Document known strengths, weaknesses and limitations of NDT methods

We will develop a synthesis of the available information concisely. The synthesis will summarize the advantages and disadvantages of the methods, past successes/failures, limitations on the use of the technology, reliability of the measurements, equipment and processing requirements, and data processing and interpretation requirements.

In addition, we will assemble a panel of experts consisting of NRRA DOT members, equipment manufacturers and consultants to assist in summarizing the best project-level uses of the identified NDTs and to prioritize the technologies and the potential defects they can address.

  • Deliverables:The results will be summarized concisely in a technical memorandum.

Task 2: Develop test plan and facility

Based on the information gathered in Task 1, an experimental test plan will be developed to evaluate the prioritized devices and defects. With the help of the MnROAD research staff and NRRA DOT representatives, the appropriate required physical facility will be devised for each defect to varying extents. As much as possible, the existing pavement sections and sensors will be used. Also, as much as possible, the required facility will be incorporated into the reconstruction of the LVR cells. If necessary, special pavement sections will be designed and constructed to accommodate the experimental test plan.

  • Deliverables: A tech memo containing the experiment design and associated facility to implement the experimental plan

Task 3: Implementation of test plan

Upon completion of the construction of the required facilities, the experimental test plan will be implemented. As much as possible, MnDOT NDT devices and expertise will be utilized to collect the data. Appropriate analyses will be carried out to address the two objectives enumerated under the objectives, i.e.,

  1. What is the extent of defects that different NDT devices can detect with sufficient confidence?
  2. What is the accuracy of the prediction of responses of pavement under different NDT devices?


  • Deliverables: A tech memo containing the results of the experimental study

Task 4: Development of guidelines for effective use of facility and best uses of different NDT devices

In close collaboration with the MnDOT and other NRRA DOTs, the following items will be developed:

  • guidelines for the best uses of the NDT devices
  • a process for future use of the facilities for periodic assessment of the capacity and sensitivity of the existing devices
  • guideline for the use of the facility for future assessment of the new technologies

  • Deliverable: A final report containing the results of different tasks and the appropriate guidelines and processes.

Task 5: Final report

A draft project report summarizing the results, findings, conclusions, and recommendations of the research will be delivered. The report will comply with MnDOT’s Editorial guidelines. The report will include an implementation plan for improving and deploying the products of the research and a draft specification in AASHTO format. Upon the feedback of the TAP, the final report will be finalized for delivery.

  • Deliverable: A final report that is finalized based on the TAP review, and a revised report that is technically complete and approved by the TL for publication.

Project team

Email the Project Team
Principal Investigator:
Soheil Nazarian, UTEP, nazarian@utep.edu
Technical Liaison: Jacob Walker, Georgia DOT, sawalker@dot.ga.gov
Project Technical Advisory Panel (TAP): Contact us to join this TAP

  • Hoda Azari, FHWA
  • Emil Bautista, MnDOT
  • Ruari Charlesworth, Highway Data Systems (UK)
  • Kyle Hoegh, MnDOT
  • Deepak Maskey, Caltrans
  • Adam O'Neill, Highway Data Systems
  • Nicholas Schaefer, Surface Systems and Instrumentation
  • Jacob Walker, GADOT (TL)
  • Matt Wheatley, Highway Data Systems

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