Retaining Wall Stabilization Using Dual Polyurethane Foam Grouts

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PROJECT OVERVIEW

A deteriorating bin-type retaining wall at an industrial facility in Alaska was exhibiting significant structural distress. Corrosion of the steel facing had led to localized soil loss and visible outward movement of the wall. Because the wall retained footings that supported critical site infrastructure, removal and replacement were not viable. Additionally, the presence of asbestos in the wall facing restricted mechanical repair options and necessitated a minimally invasive stabilization method.

CHALLENGES

Corrosion-induced soil loss through the wall face
Lateral displacement and instability of the wall
Limited access and environmental hazards due to asbestos
Need to avoid imposing additional pressure on the already distressed wall

THE SOLUTION

Working collaboratively with the site’s engineering team, a two-stage polyurethane grouting plan was developed to stabilize the retained soils and prevent further wall movement. The approach combined two distinct polyurethane foam products, each selected for its unique physical properties and suitability for specific subsurface conditions.

Near-Wall Treatment – HS010 Single-Component Foam: The initial phase involved injection of HS010, a low-expansion, single-component polyurethane foam, via permeation grouting directly behind the corroded wall facing. This material was chosen for its ability to:

Penetrate loose gravel and granular soils
Fill voids and seal leakage paths where soil loss was occurring
Minimize expansion pressure to avoid further wall deflection

Subgrade Reinforcement – HF402 Dual-Component Foam: In the second phase, HF402, a high-expansion, dual-component polyurethane foam, was injected at greater distances from the wall. This grout provided:

High-strength, rapid expansion to densify loose soils
Improved load-bearing capacity near the infrastructure footings
Long-term stabilization of the access road and footing supporting critical infrastructure

RESULTS

The dual-grout method successfully stabilized the distressed retaining wall without requiring excavation or demolition. The combination of HS010 for precision void filling and HF402 for bulk soil improvement allowed the contractor to achieve stabilization objectives while maintaining structural integrity and minimizing risk to on-site infrastructure.

OUTCOME

Stopped active soil loss and sealed wall voids
Improved bearing capacity of retained soils
Prevented further movement of wall and footing structures
Delivered a durable, minimally invasive stabilization solution under challenging site conditions

🟥 HMI Retaining Wall Stabilization Using Dual Polyurethane Foam Grouts

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