Box Culvert Stabilization and Sealing
Voids under a three-bay cast-in-place box culvert extended up around the structure, causing the sides to fail, complicating efforts to extend the culvert as part of a road-widening project. The voids were discovered after dewatering was done, requiring box culvert stabilization. Extensive tidal flow was passing under the box culvert structure, indicating that the voids extended the full length of the roadway.
The box culvert had been constructed on piles, so was stable in terms of potential for settlement. However, the voids below the structure were causing soil to erode from along the sides, which reduced support of the adjacent roadway.
The contract documents required that traffic flow undisturbed. Due to the waterlogged state of the voids, a hydroinsensitive void filling material not subject to washout had to be used. The non-cohesive soils in the area prevented more than nominal dewatering of the void below the invert elevation of the culvert.
Polyurethane injection to fill voids around culvert and stabilize the walls. High density polyurethane foam was chosen for the box culvert stabilization because of its fast reaction speed and high expansion to allow for complete void filling and ability to be placed by free-spraying into the voids at the end of the structure.
CJGeo proposed a hydroinsensitive plural component structural foam. The selected foam has the bearing capacity to withstand the loading of traffic and provide sufficient lateral support to the walls.
CJGeo completed the box culvert stabilization by void filling around the structure with polyurethane grout, which allowed construction to proceed without further delay. The work was completed in less than one day without disruption to traffic or other activities.
The placement of geotechnical polyurethane grout was done directly into the waterlogged voids. The foam’s chemical reaction is unaffected by the presence of water. After injection, the polyurethane grout expands, displacing water as it fills the voids.