Shoring Pea Gravel with Polyurethane Injection

The Challenge

Shoring pea gravel to prevent soil loss during utility box excavation.

Structural upgrades are a positive gain for building managers. These upgrades usually come about due to years, sometimes decades of problems that have resulted in the decision to invest substantial time and money to remediate the issues. To complete the upgrade is a complete balancing act that seeks to find the equilibrium between scheduling contractors, permits, coordinating with the city, minimizing downtime, and interruptions to business. When a commercial building in Sacramento, CA was upgrading its utility box, all of these factors were considered in making a decision to work with Groundworks.

The utility box installation was taking place right next to a building’s grade beam that was supported by a deep foundation system. However, below the grade beam, nearly 20ft of pea gravel was being used as fill and to aid drainage below the building. While pea gravel served this purpose extraordinarily well, to excavate the material made for a shoring nightmare that would have led to substantial soil loss underneath the foundation. So the company needed to find a solution to shore the pea gravel for excavation.

Key Facts

The Solution

Deep Strata Injection (DSI) for soil stabilization.

Groundworks presented a plan to stabilize the pea gravel using its Deep Strata Injection (DSI) process. DSI is a process where a geotechnical polyurethane is injected to stabilize soils at depth, which is a perfect solution in this case. When a geotechnical polyurethane is injected into soil, the polymer initially travels in liquid form. This travel helps the polymer fill gaps and voids prior to expansion and with pea gravel, polyurethane has excellent permeation and stabilization potential due to relatively large gaps and voids.

The Impact

Stabilized foundation for uninterrupted excavation and utility upgrade.

Groundworks’ Deep Strata Injection process successfully stabilized the pea gravel, allowing for safe and efficient excavation during the utility box installation. This solution prevented soil loss beneath the foundation, preserving the structural integrity of the building’s grade beam. The result was a seamless utility box upgrade with minimal disruption to the building’s operations, exemplifying how innovative geotechnical solutions can address complex challenges while supporting critical infrastructure upgrades.