Trench Shield Adaptation Provides Protection for Large Excavation

A Gulf Coast, Florida municipality was upgrading its airport infrastructure with the addition of a new monorail to allow for better distribution of travelers at the airport. In constructing the new monorail, the contractor would need to pour a foundation and pier structure to serve as the structural base for the system. This particular phase of the project required a 23-ft wide and 48-ft long excavation excavated to a depth of about 8-ft. As is typical for this part of the country, the contractor had classified the sandy soil as a type C-60 soil.

In addition to the poor soil conditions, the contractor would also have to account for
several adjacent structures including an existing terminal, a parking garage, and one additional adjacent building. The contractor met with NTS to discuss potential shoring alternatives for this project, as the excavation requirements presented some unique considerations. The contractor would need to provide four-sided protection the length of the excavation, while also ensuring that the soil walls were properly protected at the large width the project required.

After reviewing possible shoring options the contractor elected to use a four-sided system composed of steel trench shields. The contractor installed two standard 8-ft by 24-ft trench shields with 23-ft spreaders.  The open ends of the shield were then capped with two 8-ft by 24-ft panels.  Given the size of this excavation, the capping panels had 6-in of overlap on each side which supplied enough surface area to make the system feasible. The capping of the end panels as well as the length of the spreaders required special engineering to adapt the standard manufacturer’s tabulated data to the project and ensure compliance with OSHA standards since the two configurations represented deviations from the base tabulated data. The contractor was extremely satisfied with the equipment and solution for this project. The system could be installed using existing machinery on the job site and facilitated the fast-paced project.