Across major infrastructure projects in Europe and North America, unstable rock masses, water-bearing fault zones, and weak soft ground conditions continue to pose significant risks to excavation and slope stability. In response, contractors are seeking a self drilling anchor system that can drill through difficult geology, inject grout under high pressure, and provide immediate as well as permanent reinforcement without the need for separate casing or post-grouting operations. SupAnchor, a recognized soil nail system manufacturer and ground anchor bolt factory, has introduced the SupFRP® GFRP Hollow Injection Bolt to address these challenges head-on. This innovative drill-and-grout bolt combines the functions of a rock bolt and an injection pipe, offering high tensile capacity, excellent corrosion resistance, and full grouting capability for a wide range of geotechnical applications.
On a recent highway slope stabilization project in the Italian Alps, engineers faced a complex mix of fractured limestone and clay-rich interlayers. Conventional solid rock bolts required pre-drilling, casing, and multiple grouting steps, leading to schedule delays and increased costs. By switching to the SupAnchor GFRP Hollow Injection Bolt, crews were able to drill and grout in a single pass, achieving full encapsulation and immediate load transfer. The bolt's hollow core allowed high-pressure injection of cementitious grout, filling voids and consolidating the surrounding ground, while the integrated waved thread structure ensured superior mechanical interlock with the grout. After injection, the bolt remained in the borehole as permanent reinforcement, working together with the plate and nut at the tunnel face or slope surface.
The GFRP Hollow Injection Bolt is available in six standard models, covering outside diameters from 22 mm to 38 mm and guaranteed tensile loads from 220 kN to 490 kN. All models feature a hollow core with internal diameters ranging from 8 mm to 20 mm, enabling high-pressure grout injection and efficient air/water flushing during drilling. The use of glass fiber reinforced polymer (GFRP) provides exceptional corrosion resistance, making the bolt ideal for permanent applications in aggressive environments such as marine structures, chemical plants, and tunnels with high groundwater salinity. The low unit weight—ranging from 0.58 kg/m to 1.5 kg/m—significantly reduces handling effort and improves safety on site, especially when working at height or in confined spaces.
The table below summarizes the key technical data for the six standard models. The outside diameter includes the waved thread structure, which is an integral part of the bolt's bond mechanism. The nominal cross-sectional area is based on the characteristic stress value in the core, ensuring a conservative and reliable design basis for engineers.
| Model | Outside Diameter (mm) | Internal Diameter (mm) | Guaranteed Tensile Load (kN) | Pressure Resistance (MPa) | Weight (kg/m) |
|---|---|---|---|---|---|
| H22/230 | 22 | 8 | 230 | 18 | 0.58 |
| H25/300 | 25 | 8 | 300 | 30 | 0.79 |
| H25/220 | 25 | 12 | 220 | 5 | 0.64 |
| H28/320 | 28 | 12 | 320 | 5 | 0.88 |
| H32/360 | 32 | 15 | 360 | 5 | 1.20 |
| H38/490 | 38 | 20 | 490 | 5 | 1.50 |
All models have a tensile E-modulus of 45 GPa and an ultimate strain of 2.0%, providing a balanced combination of stiffness and ductility. The bolts can be supplied with left-hand or right-hand threads and in lengths of 2 m, 3 m, 4 m, 5 m, 6 m, 7 m, 8 m, 9 m, 10 m, or 11 m, allowing customization for specific project requirements. The high-pressure resistance on the H25/300 model (30 MPa) is particularly beneficial for permeation grouting in fine-grained soils, while the larger diameter H38/490 offers maximum tensile capacity for heavy support in deep tunnels and large-span excavations.
The versatility of the GFRP Hollow Injection Bolt makes it suitable for a wide range of geotechnical and underground construction applications. In slope stabilization, the self drilling anchor bolt can be installed through loose overburden and weathered rock without casing, reducing the number of drilling passes and improving productivity. For TBM face support and forepoling, the hollow bar anchor enables fast installation ahead of the excavation face, providing immediate ground reinforcement and controlling deformation in squeezing ground or running sand conditions. In confined ground conditions and stabilization of soft rock, the drill-and-grout bolt allows full grouting of the borehole, filling voids and improving the mechanical properties of the surrounding ground, which is critical for ensuring long-term stability.
Key application scenarios include:
From a market perspective, the global demand for reliable geotechnical reinforcement systems continues to grow as urbanization drives the construction of deeper basements, longer tunnels, and more complex infrastructure. The GFRP material's corrosion resistance addresses a key limitation of traditional steel anchors, extending the service life of structures in aggressive environments and reducing maintenance costs. This aligns with the industry's shift toward sustainable construction practices, where durability and reduced environmental impact are paramount. SupAnchor's hollow injection bolts have already been adopted in major projects across Europe, Asia, and the Americas, including metro tunnels, highway cuts, and dam foundations, demonstrating their adaptability to diverse geological conditions.
SupAnchor has established itself as a professional and innovative force in the ground anchor bolt factory segment, with a strong focus on R&D and quality assurance. The company operates ISO 9001-certified production facilities and adheres to international testing standards such as EN 14490 and ASTM F432, ensuring consistent product performance and reliability. Its engineering team works closely with contractors and consultants to develop customized solutions for challenging ground conditions, fostering a collaborative approach that has led to successful project outcomes in over 40 countries.
The launch of the SupFRP® GFRP Hollow Injection Bolt underscores SupAnchor's commitment to advancing geotechnical technology. By combining high tensile strength, pressure resistance, and corrosion protection in a lightweight, easy-to-handle package, the system offers a compelling alternative to traditional rock bolts and self drilling anchor systems. As infrastructure owners increasingly prioritize resilience and lifecycle cost, products like the GFRP Hollow Injection Bolt are poised to become standard practice in tunneling, mining, and slope engineering.
SupAnchor's self drilling anchor system delivers reliable ground stabilization for a major highway project, overcoming difficult geology and ensuring long-term safety.
SupAnchor's GFRP hollow injection bolts deliver 220–490 kN tensile loads, corrosion resistance, and full grouting for slopes, tunnels, and mining. Six models from 22–38 mm.
SupAnchor's self drilling anchor system demonstrates superior performance in a complex infrastructure project, offering rapid installation and high load capacity for slope stabilization and foundation support.
SupAnchor introduces the SupCT Bolt System, a duplex corrosion-protected self-drilling anchor bolt combining steel and GFRP variants for permanent rock support in tunnels, mines, and slopes.
A major infrastructure project deploys SupAnchor's self drilling anchor system to overcome challenging geology, ensuring stability and safety.
