As underground infrastructure expands across Europe and North America, geotechnical engineers face increasingly difficult ground conditions—fractured rock, high water inflow, and aggressive chemical environments. In response, SupAnchor, a global leader in self drilling anchor systems and hollow bar anchors, has introduced the SupCT Bolt System, a combination bolt designed for both immediate and permanent rock support.
The SupCT Bolt System is available in two main categories: Steel Bolt (including solid bar and hollow bar types) and GFRP Bolt (including solid bar and hollow bar types). Steel bolts offer high ductility and robust load-bearing capacity, while GFRP bolts provide permanent corrosion resistance and are ideal for applications where the bolt must be cut later, such as TBM tunnel faces.
On a typical tunnelling site, the installation sequence begins with drilling a borehole to the required diameter—45 to 48 mm for most standard bolts, or 64 to 68 mm for larger models. The SupCT Bolt is then inserted, and grout is pumped through the system. The optimized grouting design ensures that the end of the borehole is filled first, eliminating voids and guaranteeing complete encapsulation. This drill-and-grout bolt approach allows a single bolt to provide both temporary and permanent support, reducing the need for multiple support components and speeding up the construction cycle.
The SupCT Bolt System's duplex corrosion protection is a standout feature. Each steel rebar bolt is treated with hot dip galvanization in accordance with NS-EN-ISO 1461, followed by an epoxy powder coating per NS-EN 13438. The coated bar is then placed inside a plastic grouting pipe and fully embedded in mortar. This multi-layer system extends the service life of steel bolts from 50 years for the black type to up to 150 years for the SupCoat type. For GFRP bolts, the service life is permanent, making them suitable for highly corrosive environments such as coastal tunnels or chemical plants.
Key performance parameters for selected models are summarized below:
| Model | Type | Thread | Yield Load (kN) | Ultimate Load (kN) | Borehole Diameter (mm) | Service Life |
|---|---|---|---|---|---|---|
| SSB-M22 | Steel Solid Bolt | M22 | 239 | 300 | 45–48 | 50–150 years |
| SHB-R2712 | Steel Hollow Bolt | R27 | 246 | 270 | 45–48 | 50–150 years |
| GSB-R25 | GFRP Solid Bolt | R25 | — | 350 | 45–48 | Permanent |
| GHB-R32 | GFRP Hollow Bolt | R32 | — | 360 | 64–68 | Permanent |
Beyond load capacity, the SupCT system's factory-preassembled expansion shells reduce on-site labour and ensure thread integrity. Bolts are delivered with zinc-coated expansion shells already installed, preventing corrosion during storage and simplifying inventory management. The required installation torque ranges from 150–250 Nm for standard steel solid bolts to 200–400 Nm for steel hollow bolts, and up to 380–450 Nm for the largest GFRP hollow bolts. Pre-tension values are typically 40–60 kN, ensuring immediate anchorage upon installation.
The plastic grouting pipe features a bubble design that significantly enhances pull-out resistance. Rebar anchorage tests confirm that this design creates a mechanical interlock with the grout, transferring load efficiently from the rock mass to the bolt. Additionally, the safe bolt head design prevents mortar leakage and eliminates the risk of mortar splashing onto operators, improving site safety.
The SupCT Bolt System is engineered for a wide range of geotechnical reinforcement applications. In hard rock tunnelling, steel solid bolts such as the SSB-M22 provide high ductility and yield loads up to 239 kN, making them suitable for permanent support in road and rail tunnels. Steel hollow bolts (SHB series) allow simultaneous drilling and grouting, which is particularly effective in loose or collapsing ground where immediate support is critical.
GFRP bolts are increasingly specified for soft ground tunnelling and TBM launch and reception shafts. Their low shear strength allows tunnel boring machines to cut through them without damaging cutterheads, while their permanent corrosion resistance makes them ideal for temporary support that remains in place. The GSB-R25 solid GFRP bolt offers an ultimate load of 350 kN, while the GHB-R32 hollow GFRP bolt reaches 360 kN—both sufficient for most temporary support requirements.
From a market perspective, the SupCT system addresses a key industry need: reducing the total cost of ownership for underground structures. Traditional support methods often require separate temporary and permanent systems, leading to double installation time and higher material costs. The SupCT Bolt System's ability to provide both immediate and permanent support with a single bolt streamlines construction sequences and lowers overall project risk. For contractors in Europe and North America, where labour costs are high and environmental regulations strict, this efficiency translates directly into competitive advantage.
Furthermore, the system's protective transportation and storage features—bolts clamped in groups on pallets—minimize damage and simplify logistics. This is a subtle but important benefit for large-scale projects with hundreds of thousands of bolts.
SupAnchor has established itself as a leading soil nail system manufacturer and ground anchor bolt factory, with a portfolio that includes self drilling anchor bars, hollow bar anchors, and now the SupCT combination bolt. The company's manufacturing processes align with international standards: hot dip galvanization per NS-EN-ISO 1461, epoxy powder coating per NS-EN 13438, and GFRP testing per CSA S807, ACI 440.6M, and ASTM D7957M. These certifications assure engineers that the SupCT Bolt System meets rigorous quality and durability requirements.
The development of the SupCT system reflects SupAnchor's commitment to professional engineering, innovative design, and collaborative problem-solving. By offering both steel and GFRP options with factory-preassembled components and optimized grouting, SupAnchor enables contractors to adapt to unpredictable ground conditions without compromising safety or schedule.
As global infrastructure investment continues to rise, particularly in underground transport and renewable energy storage, the demand for reliable geotechnical reinforcement systems will only grow. The SupCT Bolt System, with its duplex corrosion protection, high load capacities, and versatile configurations, is positioned to become a preferred solution for rock support in challenging environments.
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