Stabilizing Sinking Foundation Under Thermal Storage Units

The Challenge

Concrete pads supporting thermal storage units (TSUs) at a middle school had settled and obstructed the TSUs’ connection lines.

A middle school in Denver, Colorado, utilized a pair of ice chiller thermal storage units (TSUs) for the school’s refrigeration and cooling needs. The units featured warning signs that stated if the TSU is unlevel, substantial damage and malfunction is likely to occur. To avoid this, each TSU was placed on flat, independent, reinforced concrete pads. This wasn’t enough. The school discovered that the supporting concrete slabs had settled and obstructed the TSUs’ connection lines in the process. It was of the utmost importance to the school district that the TSUs be functioning at capacity in time for the upcoming school year, so both TSUs were taken out of service for repairs.

The TSU’s were located on top of weak, expansive soils. The dry weight of the TSU with its concrete pad was 32,000 pounds (16 tons). At maximum capacity, the TSUs and their concrete pads each weighed over 133,000 pounds (56 tons). This heavy load caused the expansive soils under the TSUs to shift and render the concrete slabs unlevel. To avoid the excessive time and monetary costs of relocating each TSU, the school decided to hire Groundworks for an onsite repair using their polyurethane injections process to densify weak soil zones beneath the concrete pads.

Key Facts

The Solution

Groundworks used their polyurethane injections process to densify and stabilize soil zones beneath the concrete pads.

Groundworks took elevation profiles to determine the best locations for polyurethane injections. Once the optimal locations were determined, operators injected polyurethane injection at a three-foot depth. By using an angled injection, Groundworks crews allowed for greater material coverage to maximize TSU stability. They stabilised the weakest soil zones first and followed up with additional injections to realign the pads within the 0.75-inch tolerance requirement for the TSUs to function properly.

The Impact

In one day, Groundworks provided a timely, cost-efficient, and permanent solution for the Denver school.

In just one day, Groundworks completed the repair and immediately returned the TSUs to service. Polyurethane injections treatment increased the load bearing capacity of the soil beneath the TSUs to properly support their maximum capacity weight, and the concrete pads supporting the TSUs were re-aligned. Groundworks provided a timely, cost-efficient, and permanent solution for the Denver school.