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Implementation Assistance Application for Nondestructive Testing for Tunnel Linings (R06G)


Tunnel inspection is a challenging problem, but owners routinely need to test the integrity of the concrete lining of their tunnels to maintain and repair their assets. Tunnels typically service high-volume traffic and operate in aggressive environments. As a result, they are difficult to inspect for maintenance concerns or deficiencies such as leaks, concrete liner cracking, concrete spalling, delamination, and other debonding issues. Due to their confinement, heavy use, and the often long detours needed when they are closed to traffic, tunnels pose a unique operational challenge that technology is poised to solve.

Nondestructive testing (NDT) methods are automated, quantitative, and rapid; they provide substantially more complete coverage than conventional visual inspections. SHRP2 has evaluated all the best NDT technologies for their use in tunnel lining assessments. Ground-penetrating radar (GPR), infrared thermography analysis, and impact echo technology were determined to be the most appropriate. These technologies enable inspectors to drive through the tunnel and conduct the inspection without closing lanes.

The web-based, open-source NDToolbox helps identify and characterize testing technologies that are available to locate the primary deficiencies in tunnel linings. With the toolbox, users can explore different NDT technologies and examine their use in detecting deterioration for conditions relevant to the project. The NDToolbox describes the technology and the physical principle behind it, applications, performance, limitations, equipment, test procedures and protocols, and sample results. It also provides recommendations regarding the best technologies for a particular deterioration detection application.

The accompanying user’s manual was developed for selecting NDT technologies that can detect defects behind or within tunnel linings. The manual includes more in-depth information on equipment, test procedures, inspector’s training requirements, data management procedures, data analysis procedures, limitations, and interpretation guidelines.

Leadership Endorsement

Each application submitted from an organization or agency must have the endorsement of the Chief Executive Officer or designee. The letter of endorsement is submitted as an attachment to the application. Guidance for creating an endorsement letter appears in the application below.

Priority Ranking

When an organization or agency submits multiple applications, it must designate priority. Please rank each application in a single grouping, including all product submissions from your agency. Do not separate your organization's applications into categories for individual products, or levels of incentives (i.e., Lead Adopter or User Incentive).

For example, if your agency submits four applications (one for C02/C08/C09/C12/C15, one for R01A, one for R16, and one for R07), your agency must rank each application in priority order from 1 to 4, with 1 as the highest priority and 4 as the lowest priority. For your convenience, you will find a box later in this application to designate the priority ranking. FHWA and AASHTO will take into consideration the agency’s rankings when reviewing and evaluating the applications for implementation assistance. Your priority ranking should be expressed as "X of Y," as in "1 of 4."

Available Implementation Assistance

  • Proof of Concept
  • Up to 2
  • Up to $250,000 in the form of direct funding and/or technical assistance for implementation activities, including a national showcase event.
  • State Departments of Transportation (DOTs), Metropolitan Planning Organizations (MPOs)
  • June 27, 2014


  1. Commitment of DOT leadership to embrace NDT methods for tunnel lining inspection and incorporate condition assessment results within DOT tunnel inspection, asset management, and maintenance programs.
  2. Participation in hands-on training on the use of various NDT technologies, development of application protocols for deploying NDT technologies on routine inspections, and development of the means to incorporate NDT data in asset management programs.
  3. Identification of one or more concrete-lined or tile-on-concrete-lined tunnels to test and showcase the use of NDT technologies for concrete tunnel lining condition assessment.
  4. Participation in product evaluation activities, including an organizational, before/after assessment conducted by an independent consultant for FHWA.
  5. Willingness to share knowledge with neighboring DOTs interested in implementing NDT technologies for tunnel lining evaluations, including reporting on the lessons learned from the implementation study and efforts to use the data for asset management.
  6. Willingness to participate in regional or national knowledge sharing events to promote NDT technologies.

Application Form

Follow these steps to apply for implementation assistance:

  1. Review all background information located on this product's application page.
  2. Download the Nondestructive Testing for Tunnel Linings (R06G) application form; and save it to your computer in order to iterate, revise, and secure approvals before uploading the final application and Leadership Endorsement Letter to this site.
  3. Once you have completed this form and secured the required Leadership Endorsement Letter(s), return to application page and complete the contact information fields.
  4. Upload this form and the Leadership Endorsement Letter to the page.
  5. Click submit; you will receive an email confirmation that includes the uploaded endorsement letter and application form.
The Round 3 application period has closed.

  • View Leadership Endorsement Guidance

  • Download the Nondestructive Testing for Tunnel Linings (R06G) application form.

  • Contact Information

Be sure to click submit only one time.

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