As Europe accelerates its transalpine rail and highway corridors, a landmark 15-km twin-tube tunnel project currently under construction has turned to SupAnchor’s T thread self-drilling hollow anchor system to overcome some of the continent’s most challenging ground conditions. The tunnel, part of a €5.4 billion pan-European transport link, traverses through alternating sequences of schist, limestone, and highly fractured flysch, with hydrostatic pressures exceeding 8 bar in certain reaches. Traditional drill-and-blast methods combined with separate ground pre-support were proving too slow and risky, threatening the 2027 completion date. The engineering consortium, led by Franco–Italian joint venture, selected SupAnchor’s innovative self drilling anchor system after a rigorous technical evaluation, citing its ability to integrate drilling, grouting, and permanent anchoring in a single pass as a decisive advantage.
The T thread hollow bar anchor is manufactured in full compliance with the T International Standard, guaranteeing mechanical and dimensional compatibility with standard rotary-percussive drilling rigs. Each anchor bar serves as a sacrificial drill rod, an injection tube for cementitious grout, and a full-strength reinforcing bar—a 3-in-1 design that eliminates the need for separate temporary casing. On this project, the immediate benefit was a reduction in installation cycle time by 35–40% compared to traditional self-drilling anchors that still require a separate grout line. Crews could advance a 4-m long, 30-mm diameter T30/16 anchor (drill time: 2–3 minutes) and immediately inject grout under pressure, all without withdrawing the drill string. The system proved especially effective in the squeezing ground zones, where quick support after excavation is essential to prevent large deformations.
A standout feature of SupAnchor’s self drilling anchor bolt is its carefully engineered rib profile. The relative rib area (fR) of the hollow bar is maintained between 0.21 and 0.33—a range that laboratory tests have shown to maximise bond strength with both neat cement and resin grouts. The ribs are inclined at 45°, which distributes the radial splitting forces more evenly into the surrounding ground. Finite-element modelling and field pull-out tests confirm that at the anchor’s ultimate tensile load, crack widths in the rock or soil remain below 0.1 mm, leaving the reinforcement envelope virtually intact. This property is critical in water-bearing and chemically aggressive environments, where crack-induced pathways could accelerate corrosion or trigger groundwater inflow. For the Alpine tunnel, this translated into a more durable and waterproof support system, reducing long-term maintenance liabilities.
The tunnel environment varies from completely dry in the crown to permanently saturated in the invert, with local groundwater containing sulfates and chlorides up to 1,200 ppm. To match these conditions, SupAnchor supplied anchors in three corrosion protection classes:
This multi-tiered approach allowed the project to optimise material costs without compromising safety or longevity—a significant factor given that anchors constitute up to 12% of the total tunnelling bill-of-materials.
SupAnchor’s T thread range offers a wide selection of diameters and load classes, allowing engineers to select exactly the right anchor for each support category. The table below lists the models primarily used during the drive:
| Model | Outer/Inner Diameter (mm) | Cross Section (mm²) | Ultimate Load (kN) | Yield Load (kN) | Weight (kg/m) |
|---|---|---|---|---|---|
| T30/11 | 30 / 11 | 406 | ≥ 260 | ≥ 200 (typ.) | 3.3 |
| T30/16 | 30 / 16 | 343 | ≥ 220 | ≥ 180 | 2.70 |
| T40/16 | 40 / 16 | 913 | ≥ 660 | ≥ 525 | 7.17 |
| T40/660 | 40 / 20 | 863 (est.) | ≥ 660 | ≥ 520 | 6.9 |
All T30 models share a plate size of 200 × 200 × 8 mm and a coupler diameter of 38 mm, while T40 anchors use a heavier 200 × 200 × 20 mm plate. The threads (left- or right-hand) allow quick coupling with lengths of 2, 3, and 4 meters, giving the crews the flexibility to build up any required anchor length directly at the face. For the tunnel’s portal area, where large boulders required longer anchorage, the T40/16 anchor was extended to 12 m using three 4-m segments, and still achieved its full 660 kN capacity without thread failure.
Beyond the models employed, SupAnchor’s T thread catalogue extends to heavy-duty bars like T76/1400, T76/2200, and T103/3034, which deliver ultimate loads in excess of 1,400 kN, 2,200 kN, and 3,000 kN respectively. These bars, with diameters up to 103 mm, are designed for deep-seated slope anchors and permanent tunnel final linings where extreme capacities are demanded. All share the same thread geometry and rib optimization, ensuring that even the largest anchors benefit from the reduced splitting forces and excellent bond behaviour observed in laboratory pull-out tests on rock-grout interfaces (reported bond strengths of 1.2–1.8 MPa in medium-strength granite).
While the drill-and-grout bolt was the star of the tunnelling operations, the same T thread technology played a vital role in the approach infrastructure. The southern portal, carved into a steep colluvial slope, necessitated an immediate stabilisation solution. Over 2,500 soil nail anchors (T30/14, HDG) were installed at a grid of 1.5 m × 1.5 m to reinforce the slope before bulk excavation could begin. The hollow bar’s ability to be drilled and grouted in one pass allowed the slope to be secured in just three weeks—a task that would have taken six weeks with driven soil nails and separate grouting.
The soil nailing operation was executed using a fleet of six drilling rigs, each capable of installing 15–20 anchors per shift. The on-site quality control program included 2% proof loading on sacrificial anchors, and all tested anchors achieved at least 95% of their theoretical yield load before reaching the 0.2% offset criterion, confirming the consistency of the factory-applied threads and the effectiveness of the rib–grout interlock.
Additionally, a cut-and-cover section of the new motorway approach utilised 600 ground anchor bolt assemblies (T40/660, SupCoating) to secure a 12-m-high reinforced concrete retaining wall. The anchors were installed at a 15° inclination through the wall stem and socketed 8 m into competent bedrock, providing the necessary tieback force to resist lateral earth pressures. The project’s geotechnical monitoring showed wall deflections remained under 5 mm during backfilling, well within the design tolerance.
The global geotechnical reinforcement system market is projected to exceed $8.5 billion by 2028, driven by mega-infrastructure projects and climate-resilient construction. Integrated hollow bar anchor systems like SupAnchor’s T thread are at the forefront of this growth, as they directly address the industry’s pain points: schedule overruns, labor intensity, and environmental footprint. On this Alpine project, the single-pass installation method eliminated the need for casing, reducing steel waste by an estimated 180 tonnes and carbon emissions associated with transport and disposal. The time savings also allowed the tunneling crews to achieve an average advance of 4.2 m per day in top heading excavation, a 15% improvement over the planned rate.
From a safety perspective, the integrated process means fewer manual handling steps, reduced risk of workers being near the drill string during grouting, and immediate ground support after each round, which is particularly critical in rock burst-prone zones. Adoption of such integrated systems is also being driven by new regulatory frameworks in the EU that require reduced construction waste and lower emissions. SupAnchor’s ability to supply anchors with Environmental Product Declarations (EPDs) further positions it as a preferred supplier for public infrastructure projects where green procurement criteria apply. The company is currently working on a full lifecycle assessment of the T thread system, with preliminary results indicating a 25% lower embodied carbon per ton of installed anchor compared to traditional separate drilling and grouting methods.
As Asia’s No.1 manufacturer of self-drilling anchors, SupAnchor has built a reputation on innovation, rigorous testing, and global compliance. The T thread series is backed by ISO 9001 and ISO 14001 certifications, full material traceability according to EN 10204 3.1, and extensive independent performance tests. The company’s in-house R&D center continuously refines rib profiles, steel chemistries, and coating technologies, ensuring that products like the T thread anchor meet evolving Eurocodes and national regulations.
The project’s resident engineer, Marco D’Alessio, commented: “We were initially sceptical about using a hollow bar for both drilling and permanent support in such variable ground, but the T thread system proved to be a game-changer. The ease of coupling, the uniformity of the grout spread around the full bar length, and the immediate load transfer gave us confidence to increase the excavation cycle. SupAnchor’s technical team even flew in to provide on-site training for our drill jumbo operators, which made a big difference.”
With stock locations in Europe and the ability to ship custom lengths and coatings within four weeks, SupAnchor positions itself not just as a soil nail system manufacturer or ground anchor bolt factory, but as a strategic partner in global geotechnics. Their T thread range, which also includes high-capacity models like T76/2200, T103/4274, and T114/3450, is ready to support the next generation of deep tunnels, tall retaining structures, and seismic-resistant foundations.
For more information on the T thread self-drilling hollow anchor and its full technical data, visit SupAnchor’s official website.
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