Excavation Pit Near an Active Railroad Line Secured by a Slide Rail System with Rolling Struts and Sheeting Guide Frame

A small town located north of Houston was looking to upgrade its storm drainage system by installing a new 36-inch storm line with 48-inch casings. The project would be tasked to a well-known experienced utility Texas contractor. The project would require boring the 48-inch casings underneath an active railroad line. The bore pit would have an excavation cut of 36-ft in length, 12-ft in width, and a depth of 15-ft in which the competent person onsite had originally classified the soil as Type-B. As the excavation progressed, the soil was then classified for a second time as C-60. Once the excavation had reached 8-ft in-depth and groundwater was present; the soil was then classified for a third and final time as C-80. In addition to the poor soil conditions; the excavation site presented several challenges with a few adjacent structures. An existing and functioning railroad line would be located a few feet apart from the proposed bore pit. Running perpendicular to the railroad lines, an underground tunnel would be located east of the excavation pit just a few feet away. Additionally, a live road would be located running north of the excavation cut which contributed to the increase of pressure loads against the bore pit.

The nature of the excavation cut would require a protective system that could provide enough clearance to properly lower the bore to its pre-determined position and have adequate free space so workers could properly lower and feed the casings. Additionally, the contractor would require a device that could support the pressure loads originated from the adjacent structures while complying with the Cooper E-80 ratings. After the presentation of a few protective systems, the contractor selected a slide rail system with rolling struts and a sheeting guide frame. The slide rail system is a modular protection system that can be paired with numerous applications. For this project, steel sheets and the sheeting guide frame would be added to minimize soil disturbance and provide support along the depth of the excavation where the bore would be feeding the 10-ft casings. In addition, the rolling struts provided the ability to add additional support while allowing the contractor to adjust its placement for vertical clearance. The contractor was extremely satisfied with the modular capabilities of the slide rail and how well it paired with the sheeting guide frame as well as the rolling struts which added additional support and drastically reduced the soil disturbance.