Las Americanas Hotel Structural Underpinning

Los Angeles, CA

The Challenge

The challenge of the excavation was the need to support the load-bearing exterior wall as the footing needed to be undermined during excavation. Collapsing sands threatened the excavation of a proposed elevator shaft beneath a hotel basement.

The Solution

Groundworks proposed commercial-grade Safe Base push piers to stabilize the footing, a solution that was approved by the Engineer of Record (EOR). Permeation grouting using SoilPure grout allowed safe excavation without the need for shoring.

The Impact

The SoilPure grout permeated the sands as anticipated and successfully “glued” the sands together allowing the excavation crew to safely excavate the elevation pit without collapse. Grouting successfully stabilized the sands, allowing excavation to proceed without collapse.

Location: Los Angeles, CA

Project Type: Commercial

Repair Type: Foundation Underpinning & Excavation Support

The Challenge

Collapsing sands preventing safe excavation of an elevator shaft.

During the construction of a new elevator shaft for a hotel, the excavation was hindered by collapsing sands in the basement. The elevator shaft was to be dug 8 feet below basement grade, which would be 19 feet below parking lot grade, making the sand instability a significant risk. With only staircase access to the basement, installing traditional shoring systems was not an option, which made finding an effective stabilization solution even more urgent.

The Structural engineers original design called for helical piers, but equipment limitations made basement installation nearly impossible. Additionally, the need to support the load-bearing exterior wall during excavation was another challenge.

Key Facts

320 Ft

Wall Required Stabilization

1

Elevator Pit Location Stabilized

19 Ft

Basement Grade

20 Ft

Permeation Grout Depth

The Solution

Permeation grouting to stabilize the sand and prevent collapse.

A geotechnical engineer recommended grouting the sand to prevent further collapse during excavation. Groundworks proposed using a permeation grouting technique with Deneef SoilPure grout, a one-part solution designed to stabilize loose soils. The grout was injected to a depth of 20 feet in two rows, with injections placed 18 inches apart. Grouting was performed in 1-foot lifts to ensure even penetration and stabilization. Groundworks collaborated closely with Geocon West, Inc., the geotechnical engineer of record (EOR) on the project, and Walton Construction, the general contractor, to ensure proper coordination and execution. A pre-construction meeting was held with the general contractor, geotechnical engineer, and excavation subcontractor to align on the project goals and approach.

The Impact

Successful excavation with no collapse and minimized risks.

The SoilPure grout performed as expected, effectively permeating and stabilizing the sands. The grout “glued” the sand particles together, allowing the excavation crew to proceed with the elevation pit excavation safely. The stabilization process ensured that the excavation could be completed without risk of collapse, and the project moved forward without the need for costly shoring or delays. The successful stabilization of the sands allowed the construction of the elevator shaft to continue as planned, minimizing both risks and potential costs.