COLT Railroad US Highway 63 Overpass Design

With the resurgence of the COLT Railroad, the existing at-grade crossing at US Highway 63, a high-speed, 4-lane divided highway, became a considerable safety hazard to the traveling public. In concert with the Missouri Department of Transportation, the City of Columbia and Columbia Terminal Railroad determined that it would be most feasible to relocate the rail line to a previous alignment, with the rail line over passing the highway.

The original 16-month final design schedule was compressed to ten months due to the unexpected availability of federal funding. M&M quickly went to work designing the overpass structure, a 6-span steel girder bridge with four deck girder approach spans and two 85’ through plate girder main spans.

The substructure is founded on micropiles. Intermittent rock layers and random boulders were discovered during the geotechnical investigation. Micropile foundations were chosen for their ability to drill through these obstructions and be seated into bedrock. Lateral loads on the abutment wingwalls, and the reluctance of the micropile designer to allocate such loads to the micropile foundations required the utilization of “tension straps” to bind the wingwall footings together for the purpose of carrying lateral loads.  

The proximity of the original (and proposed) embankment to the southbound exit ramp prompted the use of a 2:1 spill slope at that location. Slope stability analysis was utilized to develop specialized construction procedures to ensure that the embankment would be built in a manner that allowed it to carry the overburden loads.

M&M successfully provided a quality design within the altered schedule.