Culvert Rehabilitation to Maximize Service Life While Minimizing Direct Costs and Traffic Disruption
(September 20, 2017)
NCHRP Staff: Waseem Dekelbab, WDekelbab@nas.edu
Research Agency: Louisiana Tech University
Principal Investigator: Eriz N. Allouche
NCHRP Project 14-19, “Culvert Rehabilitation to Maximize Service Life while Minimizing Direct Costs and Traffic Disruption” produced (1) an extensive literature review related to culvert rehabilitation and (2) interactive charts that enable users to identify applicable rehabilitation methods for defective culverts. The charts lay out a decision process for selecting assessment and rehabilitation methods that are grouped by:
- culvert materials: concrete, metal, and thermoplastic; and
- deficiency types: lacking structural stability, exhibiting bedding deficiencies, and lacking hydraulic capacity.
Literature Review Report
Installing and Opening the Charts on a Local Computer
The user can also access the charts on a local computer after installing the zip files. Three zip files have been created (concrete.zip, metal.zip, and thermoplastic.zip) each containing pdf files. The user should create a separate directory for each zip file and copy the zip file into it, then unzip the file (extract all existing files to the same directory). The zip file may afterwards be deleted. To start using the charts on the local computer, the user opens Chart 1 ("concrete_overview.pdf", "metal_overview.pdf" or "plastic_overview.pdf").
Viewing the Charts Online
Click on the buttons below to view the charts and related materials.
Using the Charts
The following four charts have been made for each of three culvert pipe types covered in this study:
Chart 1: Overview
Chart 2: Methods for Rehabilitation of Culverts Lacking Structural Stability
Chart 3: Methods for Rehabilitation of Culverts Exhibiting Bedding Deficiencies
Chart 4: Methods for Rehabilitation of Culverts Lacking Hydraulic Capacity
The methods selection process in each graph begins with the culvert deficiency ( Start Point, typically in the top left corner or top middle of the chart).
From there, the user is presented with questions ( Decision Making Points).
Based on choices made, the user navigates through the chart arriving at the problems identified to possibly cause the given culvert deficiency ( Intermediate Points) until ultimately reaching the applicable rehabilitation methods ( Conclusion Points).
Each rehabilitation method in the chart is shown as a link which opens a pdf file with the description of that method. The following topics are included for most methods: method overview, materials used, applicability, construction issues, QA/QC considerations, standards and specifications, advantages and limitations, example case histories and references. The pdf file also has links to return to the decision chart from which it was opened or other decision charts for the given culvert pipe type.
For more complete instructions with illustrative examples, please see the Instructions for Decision Making Charts (PDF).
NCHRP Project 14-19 Background
Highway infrastructure across North America is characterized by a huge inventory of damaged and decaying culverts. The cost of culvert replacement is high, and disruption to highway traffic makes conventional trench excavation undesirable. Culvert repair without trench excavation avoids problems experienced by pavements reconstructed over consolidating trench backfill.
Many pipe relining techniques have been developed to restore the hydraulic and/or structural integrity of culvert structures, and the use of these methods has increased significantly in recent years. Liners are cast in place, or pre-formed liners may be pulled into place through the culvert and grout is pumped behind the preformed liner. Methods have also been developed to undertake localized repairs, restore the integrity of the backfill behind the culvert, and repair voids caused by soil erosion.
Repair methodologies are largely driven by specialist contractors, while engineers representing infrastructure owners (structural and geotechnical consultants) generally have limited experience with these systems. Others have questions regarding the extent to which earth loads and vehicle loads reach a localized repair or full length liner. Questions also remain regarding the effect of ground loss behind repaired culverts, and circumstances requiring repair of soil voids, rather than focusing repair efforts on the culvert structure alone. As such, research was needed to (a) investigate techniques of localized or full-length culvert rehabilitation and (b) develop design procedures for cost-effective rehabilitation techniques that extend service life while avoiding disruption to traffic.