Nellis AFB Hospital Tunnel Sealing

The Challenge

1″ Floor Slab Settlement Challenges Near Utility Tunnel

The hospital’s floor slabs began to settle by up to 1 inch on both sides of a utility tunnel running beneath the building, causing concern for structural integrity. Given the hospital’s 24/7 operational status, drilling through the interior floors to address the issue was not a viable option, requiring alternative solutions to mitigate further settlement without disrupting hospital operations.

Key Facts

The Solution

Non-Intrusive stabilization using horizontal injection every 4 feet.

To determine the appropriate injection depth for stabilizing the slabs, Dynamic Cone Penetrometer (DCP) tests were conducted at six locations throughout the hospital. To avoid disrupting hospital operations, horizontal injection points were installed every 4 feet through the walls of the underground utility tunnel. This approach allowed for effective stabilization of the slabs on both sides of the tunnel without requiring intrusive drilling or work inside the hospital.

Project Support

• Project was monitored by the US Army Corps of Engineers
• Groundworks worked under United Excel, general contractor, who was performing a multi million dollar renovation to the hospital.

The Impact

Floor stabilization and densification exceeds expectations.

Although the primary scope of work focused on stabilizing the base soils to support a self-leveling overlay installation, many areas of the floor were successfully returned to level during the process. The weak base soils were effectively densified, ensuring a stable foundation and achieving improved results beyond the original stabilization goals.