Mining & Tunneling
Underground work doesn’t forgive the wrong material. Active water, fractured ground, confined access, and shift schedules that can’t slip make conventional grouting a poor fit for mining and civil tunneling. NCFI’s polyurethane grout systems are formulated for these conditions: sealing infiltration at the source, stabilizing fractured rock and soil, and filling voids where excavation isn’t an option.
How Polyurethane Grout Is Used Underground
Cement-based grouts dilute, displace, and need access that most underground sites don’t offer. Polyurethane grout works differently, and it works in the conditions mines and tunnels actually present. NCFI polyurethane is injected as a liquid through small-diameter ports drilled into rock, concrete, or soil. Once placed, it reacts on contact and expands rapidly to fill voids, fractures, and infiltration pathways with a rigid, closed-cell mass. Hydrophobic formulations push water out of the way as they cure, so they perform in active inflow conditions, not just damp ones. Because polyurethane grout can be placed through ports rather than excavation, it reaches the spaces underground work creates: behind TBM segments, inside shaft walls, deep into rock fractures, and around inaccessible void perimeters. Cure times are measured in minutes, not days, so crews can return to active work in the same shift. And once cured, NCFI polyurethane is chemically stable and won’t leach into surrounding soils or groundwater.
Warning Signs
Active Water Infiltration
Seeping joints, leaking fractures, or flowing water at a tunnel face or shaft wall that slows excavation, threatens equipment, or compromises worker safety.
Unstable or Fractured Ground
Loose material, fractured rock, or localized void zones around an active excavation that signal loss of ground confinement or inadequate support.
Voids Behind Tunnel Linings
Gaps between a tunnel segment and the surrounding rock or soil profile. Left untreated, they undermine lining integrity and create long-term settlement risk.
Settlement Above an Active Excavation Surface
subsidence, depressions, or ground movement above a working tunnel or shaft, indicating significant void development or ground migration below.
Geotechnical Product Documents
Dual-Component Systems TDS
Lightweight Fill Systems TDS
Single-Component Systems TDS
Common Uses of Polyurethane for Mining & Tunneling
Tunnel Grouting & Water Cutoff
Uncontrolled water inflow from fractured rock, a failing grout curtain, or an unsealed joint slows crews, creates safety risk, and adds cost. NCFI’s hydrophobic polyurethane grout is formulated to stop active infiltration at the source. Injected directly into the inflow pathway, it reacts on contact with water and expands into a rigid, watertight seal that holds under pressure.
Underground Void Filling
Voids behind tunnel linings, in mine drifts, or around inaccessible structures put load on the wrong places. NCFI Lightweight Fill Systems are designed for large-volume void filling. Low-exothermic expansion lets crews place material without overheating or overloading adjacent structures. For smaller, targeted cavities, dual-component systems deliver higher-density fill with a faster cure. In both cases, NCFI polyurethane conforms to irregular geometry and bonds to surrounding surfaces.
Annular Grouting for TBM Tunnels
Tunnel boring machines leave an annular space between the lining and the excavated profile. How that gap is treated determines long-term lining performance and settlement risk. NCFI polyurethane systems fill annular space and treat voids behind segments where access, schedule, or ground conditions make conventional backfill grouting impractical. The material’s expansion behavior reaches irregular geometries conventional grouts cannot, producing a more uniform tunnel envelope.
Mine Shaft Grouting & Water Control Shaft
sinking routinely encounters groundwater inflow that has to be managed before the shaft can advance. NCFI polyurethane grout seals inflow into the excavation, treats permeable zones identified during drilling, and stabilizes loose or fractured material around the shaft perimeter. It’s well-suited to the active, condition-by-condition decisions shaft work actually requires.
Localized Ground Stabilization
Fractured, loose, or water-weakened ground shows up at tunnel headings, in mine drifts, and next to excavations in mixed conditions. NCFI polyurethane is injected into the affected zone to fill the void space between rock fragments or soil particles, increasing cohesion, reducing permeability, and restoring enough ground competency for crews to work through it safely.
Mine Abandonment & Legacy Infrastructure Sealing
For shaft sealing, adit closure, and long-term water control in inactive mines, NCFI polyurethane offers a durable, chemically stable solution where re-access isn’t planned and conventional placement isn’t practical. The material’s moisture resistance and long-term stability make it a reliable choice for legacy sites that need to stay sealed.
Solutions for Any Project
NCFI polyurethane grout systems can support a wider range of underground work beyond the applications above, including:
- Rock fracture permeation grouting
- Pre-injection ahead of excavation for heading support
- Crack and joint sealing in concrete tunnel linings
- Sealing void perimeters prior to conventional backfill placement
- Containment and sealing using polyurea lining systems
- Stabilization of soil and alluvial zones adjacent to rock excavations
- Post-construction rehabilitation of underground structures
The Advantages of NCFI Polyurethane in Mining & Tunneling
Made in America
Every NCFI product is manufactured in the United States. That means a domestic supply chain you can rely on, shorter lead times, and direct support from a team that builds the product.
Training & Field Support
NCFI offers comprehensive classroom and on-site training, plus hands-on field support during project execution. When ground conditions change underground, our technical team is on the phone or on the site.
Performs in Active Water
Hydrophobic formulations react on contact with water, displacing moisture and curing in active inflow conditions, not just damp ones.
Reaches Where Excavation Can't
Injected through small-diameter ports with standard geotechnical equipment, polyurethane grout fills fractures, voids, and cavities that conventional placement methods cannot access.
Fast Cure, Fast Return to Work
Rapid reaction times keep shifts on schedule. Many treatments can be completed and active work resumed within the same shift.
Environmentally Inert
NCFI polyurethane systems are chemically stable once cured. Select formulations carry NSF/ANSI 61 certification for use near potable water systems, with no leaching into surrounding soils or groundwater.
Real-World Results
See how NCFI polyurethane grout has been used to address water infiltration, void development, and ground stabilization challenges in mining and tunneling environments.
Polyurethane Systems
Our lines of single- and multi-component polyurethane systems offer a range of densities and cure profiles to match the conditions you’re working in. Every batch meets strict testing and quality-assurance standards, so what gets to the field performs the way the spec sheet says it will.
Single-Component Systems
Single-Component Systems Hydrophobic permeation grouts formulated for soil stabilization, void filling, joint sealing, and infiltration control.
Explore ProductDual-Component Systems
Dual-Component Systems High-density, fast-cure systems for targeted water cutoff, structural void filling, and ground stabilization.
Explore ProductLightweight Fill Systems
Lightweight Fill Systems Dual-component systems formulated for low exothermic heat, ideal for large-volume cavity filling and layered placement.
Explore ProductFrequently Asked Questions about Polyurethane Injection for Mining & Tunneling
Cement grout can be diluted or displaced by water before it sets, which limits it in active inflow. Polyurethane grout is hydrophobic: it reacts with water, expands to fill the void or fracture, and cures to a rigid, stable mass. It sets in minutes, fits through smaller ports, and reaches fractures cement slurry can’t penetrate.
NCFI polyurethane reacts exothermically during installation, so any use in methane-present environments requires a site-specific safety evaluation covering ventilation, heat generation, and applicable MSHA standards. Our technical team can support that evaluation.
Select NCFI polyurethane systems carry NSF/ANSI 61 certification. Once cured, they’re chemically stable and do not leach into surrounding soils or groundwater. Contact us to confirm which formulations are certified for your application.
Select NCFI geotechnical polyurethane systems carry fire-resistance characteristics and may meet applicable ASTM fire-performance standards depending on formulation. Fire-rated performance is product-specific. Contact us to identify the right system for your project requirements.
In mining, mining engineers, geotechnical engineers, and operations managers are usually involved. In civil tunneling, design engineers, EPC contractors, and project owners specify the approach. NCFI works with all of them, providing technical documentation for engineering teams and training and field support for the contractors doing the work.
Yes. NCFI provides classroom and on-site training covering polyurethane behavior, injection design, equipment, and application-specific techniques. Our technical team is also available for field support during execution. Contact us to discuss options for your crew.
Each line is built for different conditions. Dual-Component Systems are high-density and fast-curing, best for targeted water cutoff, structural void filling, and ground stabilization. Lightweight Fill Systems handle large-volume filling where low heat generation matters. Single-Component Hydrophobic Systems are permeation grouts for fine-grained or fractured materials. Our technical team will help you match the system to the conditions.
About Us
NCFI has been a global leader in polyurethane foam production since 1964. We opened our geotechnical division in 2008 to bring that manufacturing expertise directly to ground control, water management, and underground stabilization. Our systems are US-manufactured, rigorously tested, and backed by a technical team available at every stage of the project, from initial specification through field application. We understand the challenges you face underground. We’re here to help.
We Have Partnership Down to a Science
We understand the challenges you face, and we’re here to help. Reach out today, and let's work together to find the best solution tailored to your needs with the highest-quality polyurethane foam products available.