Slide Rail System Provides Paramount Support on a Bridge Replacement Project

Recently a contractor was tasked to replace an existing bridge located in the Iron and steel state of Alabama. The new structure would be constructed adjacent to an existing bridge allowing the contractor to minimize the footprint disturbance of the existing highway. The initial phase of the project would require the construction of a bridge footer located on opposite sides of the river and a few feet away from the existing footer of the aging bridge infrastructure.

The new footer would be composed of bents and bents caps designed to provide additional support between the bridge spans while resisting vertical and lateral loads created by moving vehicles. The footer would be constructed via poured in place for which the contractor would have to dig two excavation pits on opposite sides of the river. Both pits would measure 20-ft in length with a width of 20-ft and a depth of 16-ft that the Competent Person on-site classified the sandy clay soil as C-60.

The project site presented a challenge with the limited workspace area that needed to be leveled as the terrain found around the river presented a slip-off slope landscape. The river would also be a main point of concern, as it is known to overflow from its banks. A shoring system would have to secure the sections facing the river and provide proactive support from the pressure loads exerted by the existing bridge structure while maintaining the exact configuration during the pour as the work area would be limited. In addition, the contractor would require a system with a small footprint so that a small excavator and crane could operate efficiently during the installation. The challenges forced the contractor to look for a proactive solution for the underground work and contacted NTS for assistance. NTS evaluated all of the challenges and presented an action plan utilizing a slide rail system. The slide rail system provided the best clear span area and allowed the contractor to use the same configuration on all pour-ins while providing proactive support around the excavations. In addition, the system permitted the panels to sit flush to the existing bridge structure while shielding the sections facing the river on one of the sections of the pour-ins. The slide rail system provided paramount protection during the construction of the bridge footer and provided the proper clearance in a tight space area.