A Northwest Florida contractor was tasked to install 180-lf of a 60-inch pipe casing via boring. The project required a linear run of 60-ft with a width of 20-ft and a depth of 16-ft in a sandy clay mixture that the Competent Person classified as Type-C-60.
The project site presented several challenges that could negatively impact the integrity of the adjacent structures. The excavation was located in line to a highway overpass involving a high traffic roadway and several highway overpass columns. The project would require a protective system that could properly accommodate a bore pit with a desired 41-ft open span work area for a 60-inch bore casing pipe running between the overpass support columns. Additionally, the protective system would need to address the possibility of dewatering the open trench and dealing with a deflection of the internal bracing.
The contractor called NTS to discuss a few protective options and after carefully reviewing some of the challenges, the contractor selected a site-specific slide rail and a hydraulic excavation brace combination system. Site-specific engineered systems are designed for those unique and large-scale projects where poor soil conditions and adjacent structures are present. Site-specific engineered systems offer a high degree of customization that allows for certain protective devices to be customized for unique applications. For the boring pit, it was determined that a slide rail system would be the most optimal solution that could provide a large open-span work area if supported by an excavation brace. A slide rail system is a versatile protective underground system that can be used for a wide range of applications and paired with several modular components. A hydraulic excavation brace can be used as a four-sided application composed of adjustable hydraulic brace legs designed to support rectangular and square underground excavations. For those complex jobs, braces can be used in additional polygons such as 5-sided or 6-sided excavations. The contractor was extremely satisfied with the safety provided by the site-specific engineered system, as it provided a practical solution during the pipe casing installation.