In the demanding world of underground construction and geotechnical engineering, the ability to install reliable ground support quickly and safely often determines project success. Soft rock, clay, and loose soils present persistent challenges: boreholes collapse, drilling and anchoring are time-consuming, and conventional steel anchors can obstruct later excavation. SupAnchor, a recognized ground anchor bolt factory and soil nail system manufacturer, has responded with the SupAnchor® GFRP SDA Bolt—a self drilling anchor system that integrates drilling, grouting, and anchoring into a single operation.
The new self drilling anchor bolt is engineered for permanent applications in soft ground, offering high torque resistance, high end loading, and easy handling. Its central hollow core permits water flushing during drilling and subsequent grout injection, eliminating the need for separate casing and speeding up installation. Available in ISO standard thread profiles R25, R28, R32, and R38, the system provides a versatile geotechnical reinforcement system for face stabilization, forepoling, slope stabilization, and roof or wall bolting.
The SupAnchor GFRP SDA Bolt is a hollow bar anchor that combines the functions of a drill rod, casing, and anchor in one component. During installation, the bolt is rotated and advanced using a standard drill rig. Water or air can be flushed through the central hole to cool the bit and remove cuttings, which is especially important in clayey or silty soils where clogging can occur. Once the desired depth is reached, cementitious grout is injected through the same central passage, filling the annular space around the bolt. Because the grout flows from the bottom up, the borehole is completely filled, ensuring a strong mechanical and chemical bond with the surrounding ground. This drill-and-grout bolt method is faster and more reliable than traditional two-step systems that require casing and separate anchor installation.
The GFRP (glass fiber reinforced polymer) material offers significant advantages over steel. It is lightweight, corrosion-resistant, and cuttable, meaning that during tunnel enlargement or excavation, the protruding portion of the anchor can be easily cut without damaging roadheaders, tunnel boring machines, or other equipment. This cuttability reduces downtime and maintenance costs, making the system ideal for sequential excavation methods (SEM) and soft ground tunneling.
The SupAnchor GFRP SDA Bolt is available in four diameters—25 mm, 28 mm, 32 mm, and 38 mm—each with a corresponding ISO thread profile (R25, R28, R32, R38). The table below summarizes key technical parameters for the standard lengths (from 2 m to 11 m in 1 m increments).
| Model | Outside Diameter (mm) | Internal Diameter (mm) | Guaranteed Tensile Load (kN) | Torsion Strength (Nm) | Weight (kg/m) | Thread Type (ISO) | Length Options (m) |
|---|---|---|---|---|---|---|---|
| H25S | 25 | 12 | 220 | 180 | 0.63 | R25 | 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 |
| H28S | 28 | 14 | 280 | 250 | 0.86 | R28 | 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 |
| H32S | 32 | 15 | 365 | 360 | 0.99 | R32 | 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 |
| H38S | 38 | 20 | 490 | 450 | 1.33 | R38 | 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 |
For example, the H32S model has a guaranteed tensile load of 365 kN and a torsion strength of 360 Nm, making it suitable for high-load ground support in demanding conditions. The H38S offers up to 490 kN tensile load with a larger 20 mm internal bore, allowing higher grout flow rates and faster installation. All models feature a 45 GPa tensile E-modulus and an ultimate strain of 2.0%, providing a balanced combination of strength and ductility. The waved thread structure on the outside improves the mechanical interlock with the grout, enhancing load transfer and pull-out resistance.
Because the anchors are manufactured from GFRP, they are inherently corrosion-resistant, making them ideal for permanent applications in aggressive environments such as coastal slopes, acidic soils, or areas with high groundwater salinity. Unlike steel anchors, they do not require additional protective coatings or cathodic protection, reducing long-term maintenance costs.
The SupAnchor GFRP SDA Bolt is designed for a wide range of geotechnical applications where soft ground or collapsing boreholes are a concern. In tunnel face stabilization, the bolts are installed through the tunnel face in a fan pattern before excavation. The self drilling anchor system provides immediate support, preventing face collapse and allowing safe excavation in clay, silt, or highly fractured rock. The central flushing hole is particularly effective in these conditions because it prevents the borehole from collapsing during drilling, a common failure mode with conventional methods.
For forepoling (also known as spiling), the bolts are installed ahead of the tunnel face at a slight upward angle to create a protective umbrella. The self drilling anchor bolt is advanced into the ground with simultaneous drilling and grouting, forming a reinforced arch that supports the ground above the excavation. This technique is widely used in urban tunneling beneath buildings or infrastructure, where settlement control is critical.
In slope stabilization, the bolts can be installed vertically or at an angle to reinforce unstable slopes, retaining walls, or landslide-prone areas. The lightweight GFRP material reduces the equipment needed for installation, and the permanent corrosion resistance ensures long-term performance without maintenance. The system is also suitable for roof and wall bolting in mines and underground caverns, where the cuttability of the anchor avoids interference with mining equipment.
As governments and private developers invest billions in transportation, water management, and mining infrastructure, the need for reliable and efficient ground support systems has never been greater. Traditional ground anchoring methods often require multiple steps: drilling with casing, removing the casing, inserting the anchor, and then grouting. This process is slow, labor-intensive, and prone to borehole collapse in soft ground. The SupAnchor GFRP SDA Bolt eliminates these problems by combining all steps into one continuous operation, reducing installation time and improving safety.
According to SupAnchor, the drill-and-grout bolt can reduce installation time by up to 50% compared to conventional systems, leading to significant cost savings on large projects. The system's compatibility with standard ISO threads means that contractors can use their existing drilling equipment without modification, further lowering the barrier to adoption. The lightweight nature of the anchors (0.63–1.33 kg/m) also reduces transportation and handling costs, especially on remote sites.
Furthermore, the use of GFRP avoids the problem of steel corrosion, which is a major cause of anchor failure over time. In permanent applications such as slope stabilization or tunnel linings, corrosion can compromise the structural integrity of the anchor and lead to costly repairs. The SupAnchor GFRP SDA Bolt offers a maintenance-free solution with a design life that matches the service life of the structure.
SupAnchor has established itself as a leading soil nail system manufacturer and ground anchor bolt factory, with a strong focus on research and development. The company's engineers have developed the GFRP SDA Bolt to meet the stringent requirements of European and North American standards, including ISO thread profiles that ensure interchangeability and reliability. The product is manufactured under strict quality control, with each batch tested for tensile strength, torsion resistance, and dimensional accuracy.
The company's commitment to innovation is reflected in the design of the waved thread structure, which increases the bond strength between the anchor and the grout without increasing the outer diameter. This feature, combined with the central flushing hole, makes the SupAnchor GFRP SDA Bolt a true geotechnical reinforcement system that adapts to a wide range of ground conditions.
SupAnchor's products have been used in numerous infrastructure projects worldwide, including highway tunnels, metro systems, mining operations, and slope stabilization projects. By providing reliable and cost-effective ground support, SupAnchor contributes to the safety and efficiency of these critical works.
With the introduction of the GFRP SDA Bolt, SupAnchor continues to lead the industry in self drilling anchor system technology, offering engineers and contractors a versatile, high-performance solution for the most challenging ground conditions. For more information about the SupAnchor GFRP SDA Bolt, including detailed technical data and project references, please visit the official SupAnchor website.
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