Beam and Plate System Shores 36′ Depth Excavation

 The contractor was performing a project to connect new sanitary sewer infrastructure, as well as replacing an existing manhole, to improve flow and efficiency. The contractor’s competent person had classified the clay soil as a Type B soil at the top of excavation and transitioning towards a Type C-60 soil as the depth increased.

The project would require a 36-ft depth, which was compounded by the fact the excavation would need to occur within a 4-way intersection between two busy local streets. In addition to the depth of the excavation, the contractor would need to perform three sanitary sewer connections at varying heights along the structure. The location relative to the streets would make it difficult to lay the soil back to slope a portion of the excavation, so the contractor wanted the shoring system to handle the entire depth of the excavation.

The contractor contacted NTS to discuss options for providing shoring to the total depth of the project. After an initial review of possibilities, the contractor elected to utilize an engineered beam and plate system. NTS presented an engineered trench safety plan covering the use of the steel beams and plate to ensure that the system would be safe for the crew while performing the work, as well as satisfying a local requirement for site-specific engineering on deeper excavation projects. The beam and plate system was installed by drilling pilot holes to the required depth and then inserting beams through the holes. Steel plates were then pushed to depth between the channels within the beams to provide the required lateral protection against the excavation’s walls. As the excavation proceeded steel walers were welded across the walls to provide additional support according to the engineered plan.

The contractor was very impressed with the shoring system and the productivity benefits gained from the system. The use of the steel plates, for instance, saved a considerable amount of time over timber shoring, which had also been considered.