In a recent infrastructure project involving a soft ground tunnel beneath a major city, engineers faced severe challenges: water-saturated clay and unstable sand layers threatened face stability and construction timelines. Traditional support methods required cumbersome casing and multiple steps, but the project turned to a cutting-edge solution—the SupFRP® GFRP SDA (Self-Drilling Anchor) Bolt from SupAnchor®. This self drilling anchor system integrates drilling, grouting, and anchoring into a single operation, enabling rapid installation and immediate ground support. Its successful deployment not only accelerated the project but also demonstrated the transformative potential of advanced geotechnical reinforcement systems in modern civil engineering.
As urbanization expands and infrastructure ages, the demand for efficient and reliable ground support in tunnels, slopes, and deep excavations continues to rise. SupAnchor, a leading manufacturer of soil nail systems and ground anchor bolts, has responded with the GFRP SDA bolt—a hollow bar anchor that simplifies operations while delivering exceptional performance in the most demanding conditions.
The SupFRP® GFRP SDA Bolt is a self drilling anchor bolt designed for use in soft rock, clay, and mixed ground formations. Its defining feature is a central flushing hole that allows water to be injected during drilling, clearing debris and cooling the bit. Once the desired depth is reached, the same central channel serves as a conduit for cementitious grout, transforming the hollow bar into a permanently bonded anchor. This all-in-one process eliminates the need for separate drilling rods and casing, reducing installation time by up to 50% compared to conventional methods.
Manufactured from glass fiber reinforced polymer (GFRP), the bolt offers high tensile strength and corrosion resistance, making it suitable for permanent applications without the risk of rust or chemical degradation. Unlike steel alternatives, GFRP is also cuttable, meaning it can be easily sliced by tunnel boring machines or roadheaders during subsequent excavation phases—a critical advantage in sequential excavation methods or when future enlargement is planned. This feature protects expensive machinery from damage and avoids costly delays.
SupAnchor’s engineers have refined the waved thread profile along the entire length of the bolt, ensuring optimum load transfer from the ground to the anchor body. The threads conform to ISO standards (R25, R28, R32, R38), guaranteeing compatibility with standard drilling equipment and couplers worldwide. The result is a drill-and-grout bolt that delivers high torque resistance during installation and high end-bearing capacity under load.
To meet diverse project requirements, the GFRP SDA bolt is available in four diameters, each offering a balanced combination of mechanical properties. The table below summarizes key parameters for the H25S, H28S, H32S, and H38S models:
| Model | Nominal Diameter (mm) | Guaranteed Tensile Load (kN) | Torsion Strength (Nm) | Weight (kg/m) | Thread Type (ISO) |
|---|---|---|---|---|---|
| H25S | 25 | 220 | 180 | 0.63 | R25 |
| H28S | 28 | 280 | 250 | 0.86 | R28 |
| H32S | 32 | 365 | 360 | 0.99 | R32 |
| H38S | 38 | 490 | 450 | 1.33 | R38 |
These figures highlight the extraordinary capacity of the GFRP hollow bar anchor. For instance, the H38S model delivers a guaranteed tensile load of 490 kN, equivalent to supporting nearly 50 tonnes of suspended weight, while the torsion strengths ensure reliable drilling without thread failure even in abrasive ground. The lightweight nature of GFRP—as low as 0.63 kg/m for the smallest diameter—simplifies handling on site and reduces transport costs. All models feature an ultimate strain of 2.0% and an elastic modulus of 45 GPa, providing a stiff yet ductile response that enhances safety under dynamic loading.
The internal diameters (12–20 mm) allow for efficient grout flow, and the nominal cross-sectional areas (250–540 mm²) are calculated based on the characteristic stress in the glass fiber core, ensuring consistent performance. With standard lengths available from 2 to 11 meters (and custom lengths upon request), project managers can precisely tailor the ground reinforcement to the in-situ conditions.
The versatility of the SupAnchor self drilling anchor system has made it a preferred choice for a wide array of geotechnical challenges. In tunneling, it is routinely employed for face stabilization in soft ground and as forepoling ahead of the tunnel face to create protective canopies. During slope stabilization, the hollow bar anchor is installed at intended angles to reinforce loose overburden or weathered rock, mitigating landslide risks. In mining, it serves as permanent roof and wall bolting, securing underground openings against collapses.
One notable application involved the construction of a high-speed rail tunnel through karstic limestone with frequent clay-filled cavities. The project team used H32S self drilling anchor bolts as systematic face support. The ability to drill and grout in a single pass prevented water inflows and filled cavities, maintaining face integrity and allowing safe excavation. Similarly, on a highway widening project in a mountainous region, H38S anchors were installed as soil nails to reinforce a steep cut slope in residual soil, effectively preventing erosion and shallow failures.
The cuttability of GFRP has proven particularly valuable in urban tunneling beneath existing infrastructure. By eliminating steel obstructions, contractors avoid the risk of damaging tunnel boring machines (TBMs) and reduce downtime for cutterhead interventions. This feature, combined with permanent corrosion resistance, makes the SupAnchor drill-and-grout bolt a sustainable long-term solution for infrastructure that must endure for decades without costly rehabilitation.
Behind the performance of the GFRP SDA bolt lies SupAnchor’s unwavering commitment to research and development. As a global manufacturer of soil nail systems and ground anchor bolts, the company invests heavily in advanced composite materials and manufacturing processes. Its production facilities are ISO 9001 certified, and products undergo rigorous testing to meet or exceed international standards such as EN 14490 and ASTM. This dedication to quality ensures that every self drilling anchor bolt leaving the factory delivers consistent, predictable performance in the field.
SupAnchor also provides comprehensive technical support, from initial design to on-site installation training. By collaborating closely with consulting engineers and contractors, the company tailors solutions to the specific geological and loading conditions of each project. This collaborative approach has earned SupAnchor a reputation as a trusted partner in landmark projects across Europe, North America, and Asia.
The introduction of the GFRP SDA bolt underscores the industry’s shift toward smarter, more sustainable construction practices. By reducing material usage, minimizing waste, and lowering energy consumption during installation, the system contributes to greener infrastructure development. As cities continue to grow and the need for resilient underground space expands, such innovative geotechnical reinforcement systems will play a central role in building a safer, more connected world.
In conclusion, SupAnchor’s SupFRP® GFRP SDA Bolt represents a leap forward in ground engineering. By combining drilling, grouting, and anchoring in a single, lightweight, and cuttable element, it empowers engineers to overcome the toughest ground conditions with speed and confidence. For professionals seeking a reliable, high-performance hollow bar anchor, SupAnchor delivers—true to its brand promise of being professional, innovative, and collaborative.
SupAnchor's self drilling anchor system played a key role in stabilizing a steep slope for a new highway tunnel in the Alps, overcoming complex geology and ensuring long-term safety.
SupAnchor's GFRP SDA bolt offers a one-step drilling and grouting solution for soft ground tunnels and slopes, providing high tensile strength and corrosion resistance.
SupAnchor's self-drilling anchor system provided essential geotechnical reinforcement for a highway widening project in unstable Alpine terrain, ensuring long-term slope stability and safety.
SupAnchor's SDA grout pumps Sup2000/5000 deliver high flow (up to 6000 L/h) and pressure (6.0 MPa) for injection, anchor mortar in tunnels, mining, and shoring. Remote-controlled, durable.
SupAnchor's self drilling anchor system provides efficient ground stabilization for the challenging geological conditions of the Interstate 70 expansion project.
