Self-Drilling Anchor System Speeds Critical Highway Tunnel Reinforcement in the Swiss Alps

In the heart of the Swiss Alps, a vital highway tunnel is undergoing its most significant structural upgrade in decades. Serving as a key artery for trans-European freight and passenger traffic, the 5.2 km twin-bore tunnel had begun to show signs of geological stress in sections intersecting fractured schist and water-bearing fault zones. To extend service life and meet modern safety standards, the project owner—a consortium of European infrastructure funds—specified a comprehensive reinforcement program combining rock bolting, shotcrete lining, and drainage improvements. At the core of this effort is a self drilling anchor system supplied by SupAnchor, chosen for its ability to penetrate unstable ground while simultaneously grouting, eliminating the need for casing and dramatically reducing installation time.

Geological Hurdles Demand a One-Pass Solution

The tunnel’s mid-section passes through heavily sheared phyllite and graphitic schist, where conventional drilling often led to borehole collapse before anchor insertion. Traditional drill-and-grout methods required multiple passes, slowing progress to less than 2 linear meters per shift. The project team turned to a geotechnical reinforcement system based on hollow bar anchors, which serve as both drill rod and anchor tendon. “We needed a system that could drill, grout, and tension in one continuous operation,” explained Dr. Lorenz Meier, the project’s chief geotechnical consultant. “SupAnchor’s self drilling anchor bolt not only met that need but also offered the tensile strengths we required for permanent support.”

SupAnchor’s SDA series hollow bar anchors feature a continuous internal bore that allows flushing water or grout to be injected through the bar during drilling. This action consolidates the surrounding ground, increases skin friction, and prevents hole collapse. The anchors were installed in 12-meter lengths using a hydraulic rotary-percussive drill rig, with cementitious grout pumped at pressures up to 1.5 MPa to fill fissures and bond the bar to the rock mass.

Technical Parameters and On-Site Performance

The design called for a minimum anchor tensile strength of 550 kN, with a working load of 300 kN under permanent conditions. SupAnchor supplied its R32-400 hollow bar anchors, which feature a 32 mm nominal outer diameter and a 400 N/mm² steel grade. These bars were complemented by sacrificial anodes and an epoxy-coated sleeve over the free-length to provide double-layer corrosion protection in the aggressive alpine water (pH 5.8–6.4, with elevated sulfate).

The following table summarizes the key product parameters for the anchors used in the project:

The self drilling anchor system’s installation speed proved critical. Using the hollow bar anchor as a drill-and-grout bolt, crews advanced up to 8 linear meters of anchor installation per shift—four times faster than the previous method. “The one-pass system also improved safety because we weren’t tripping pipe in and out of collapsing boreholes,” said site supervisor Marco Bianchi. “Plus, the grout flush through the bar carried cuttings out, reducing clogging.”

Where overhead clearance was limited, the compact design of the self drilling anchor bolt allowed use of smaller crawler drills without sacrificing penetration rate. This adaptability is a hallmark of SupAnchor’s soil nail system manufacturer capabilities, which cater to both soil and rock conditions.

Industry Value: Setting a Benchmark for Alpine Infrastructure Rehabilitation

The project aligns with a broader European push to modernize aging transport corridors. With over 400 km of transalpine tunnels requiring structural upgrades by 2035, the demand for reliable ground anchor bolt factory direct supply is surging. Self drilling anchor for retaining walls and tunnel linings are increasingly specified because they shorten construction time and reduce the environmental footprint—a key consideration in sensitive alpine environments where access and noise restrictions are severe.

“This tunnel project demonstrates how modern ground stabilization anchor system can extend asset life by at least 30 years with minimal traffic disruption,” noted Dr. Meier. The anchors’ double corrosion protection package is designed for a 120-year service life in moderately aggressive soils, which aligns with European design codes for permanent underground structures (EN 1997-1 Eurocode 7).

Moreover, the successful application at this site has sparked interest from adjacent rail tunnel operators, who are evaluating self drilling bolt for civil engineering use to secure portals in weathered rock. The versatility of the hollow bar anchor as both a rock bolt for underground mining and a micropile hollow bar anchor means it can be deployed for similar projects worldwide.

SupAnchor’s role as an anchor bolt system for geotechnical engineering provider underscores the shift toward integrated solutions. Rather than selling discrete components, the company supplies complete systems including coupling nuts, centering spacers, and drilling bits engineered for optimal performance with their bars. This compatibility minimizes on-site improvisation and ensures consistent quality.

SupAnchor: Engineering Confidence from Factory to Field

Founded in 2007, SupAnchor has grown into a leading ground anchor bolt factory with ISO 9001 and ISO 14001 certifications. The company operates from a 15,000 m² manufacturing base in China and exports to over 30 countries. In the Alpine tunnel project, SupAnchor provided full technical support, including custom drill-bit configurations for the abrasive schist and on-site training for the Italian drilling crew.

“We don’t just sell steel bars; we deliver a self drilling anchor system that saves time and protects workers,” said SupAnchor’s European technical manager, Andreas Berger. “Our R32-400 bar with zinc-rich coating and epoxy has now been proven in freeze-thaw and wet conditions typical of high-altitude tunnels.”

The company’s commitment to innovation is reflected in its expanding product line: SDA bars up to R51-550 for heavy foundation loads, multi-strand ground anchor systems, and rock bolts for underground mining with yielding elements for squeezing ground. Every product undergoes full-scale tensile and fatigue testing before dispatch.

Looking ahead, the project team plans to monitor anchor loads via a distributed fiber optic sensing system embedded in the shotcrete lining. Early data suggests the hollow bar anchors are performing within 10% of the designed load, with no signs of corrosion or relaxation after six months of service.

As infrastructure budgets tighten and environmental regulations tighten, the ability to stabilize slopes, repair tunnels, and reinforce foundations with a single, efficient machine pass gives self drilling anchor systems a competitive edge. For this Swiss highway tunnel, it means a safer route for decades to come—and a blueprint for similar projects from the Andes to the Himalayas.