Abstract Manager

Culverts are critical assets within Canadian highway networks, and a significant portion of public expenditure is directed towards culvert maintenance, rehabilitation, and replacement programs to ensure that transportation networks operate at an acceptable level of service. Much of this budgetary allocation is directed towards large bridge-sized culvert structures due to their importance and complexity; as such, there is a strong desire to maximize the service life of large culverts to optimize fiscal year expenditures and reduce construction-related impacts to the traveling public, industry, and emergency services. The topic of this study pertains to a 14-year-old cast-in-place reinforced concrete box culvert located on NB Route 8 at McBean Brook near Fredericton, New Brunswick. This structure was constructed in 2010-11 during the Route 8 Bypass project and consists of a 2.6m-by-3.6m double-cell rectangular box culvert constructed beneath 25m of fill using an induced trench. Post-construction, routine visual inspections revealed that the culvert had experienced considerable cracking, which was thought to be unusual given the age of the structure. Cracking appeared to worsen over time due to progressive staining and build-up of sediment deposits, to the point that structural concerns were hypothesized. In 2023, NBDTI retained a specialized consulting team to further assess the condition of this structure. To complement on-going traditional visual inspections, the consulting team employed a number of modern instrumentation and monitoring techniques: 1) thirty-two vibrating wire earth pressure cells installed along the culvert perimeter during construction were revived and were configured to record earth pressure at one-hour intervals using an autonomous data acquisition system, 2) the groundwater level in the vicinity of the structure was recorded in three monitoring wells at one-hour intervals using autonomous data-logging equipment, and 3) high resolution photogrammetry was used for crack mapping analysis of the box culvert. The experimental results and conclusions attained from 365-days of monitoring at this site are described in this article. Results obtained from this instrumentation and monitoring program have allowed the owner to pursue an informed decision-making process regarding continued operation and on-going maintenance and rehabilitation works at this critical highway structure.