In Cape Canaveral, Florida, a heavily loaded slap stand structure was planned for construction along a transfer aisle in the Vehicle Assembly Building (VAB). This slap stand would be critical in servicing the proposed Space Launch System vehicle (SLS). However, the project faced a significant challenge when it was discovered that the near-surface subsoils consisted of loose fill materials susceptible to further densification and volume loss due to vibrations and water infiltration. With the slap stand tentatively designed to bear directly upon the ground-level floor slab of the VAB, the degree of subsoil support beneath the floor slab section became a critical concern.
To address this issue, the geotechnical engineer of record recommended a ground improvement solution using permeation grout. Helicon, a leading soil stabilization contractor, worked alongside the geotechnical design team to develop a permeation grout program that would meet the building code load criteria. AP Soil 600, a high-strength, hydro-insensitive structural polyurethane foam, was selected as the ideal product for this project due to its exceptional ability to support heavy structures.
Helicon’s technicians installed permeation grout injection pipes on a center-to-center spacing of approximately 2 feet across each of the slap stand areas. The injection points were driven to a depth of at least 5 feet below the floor slab grade. Grout was injected at a relatively low pressure (less than 50 psi), and grout needles were slowly withdrawn during pumping to ensure a uniform distribution of grout to about 3 feet below the bottom of the slab level. The amount of grout used was carefully controlled, with less than 15 gallons per foot per injection point.
The permeation grout project was a resounding success, effectively improving the load-bearing capacity of the existing soils at the site. The precise application of AP Soil 600 ensured that the slap stand structure would have a stable and reliable foundation, allowing for the safe and efficient servicing of the Space Launch System vehicle. Thanks to Helicon’s expertise and the power AP Soil 600, this piece of critical infrastructure in Cape Canaveral was reinforced and readied for countless future space exploration missions.