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.
Research was performed under NCHRP Project 14-19 by the Louisiana Tech University to develop a handbook that provides up-to-date guidance to assess the existing condition of culverts; provides assistance in the selection and design of suitable rehabilitation options; and provides information on various methods of construction associated with culvert rehabilitation.
The products developed under the Phase I are: (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. Both products are available at: http://onlinepubs.trb.org/onlinepubs/project14-19/index.html
(NCHRP Staff: Waseem Dekelbab)