Understanding Causes of Concrete Culvert Pipe Joint Separation

Project summary:

Nearly 80 percent of culverts in Minnesota are concrete pipes. The most common distress affecting these culverts is joint separation between culvert segments. This may allow water and soil to seep through the pipe, leading to loss of soil support that may ultimately result in roadway settlement and failure of the pipe. However, the cause of joint separation is unclear, so mitigation and construction practices that would minimize this problem have yet to be proposed. Thus, the purpose of this research is to determine the likely causes of joint separation in concrete culverts. The research will include a field survey of concrete pipes that exhibit joint separation. Correlations between joint separation and relevant site conditions, structural conditions, construction practices, and joint details will be established. The field data will be supplemented by detailed geotechnical and live load test data on ten concrete culverts conducted as part of an existing MnDOT implementation project regarding live loading of culverts. Computational models of the culverts will be developed to examine how the structure responds to traffic live loading, differential settlement, freeze-thaw of water in the joint, or swelling of freezing fine soils (e.g., silts and clays). Project objectives are as follows:

1. Survey a subset of concrete culverts throughout the state, recording joint separation and other pertinent site conditions.

2. Model soil-culvert systems to examine different conditions that may lead to joint separation.

3. Propose metrics to help predict risk of joint separation.

4. Develop appropriate mitigation/construction measures to address issue.