Overcoming loose ground with smart support
- Topics:
- Customer stories
- Published:
- 30 January 2026
- Text
- Andrea Hirling
- Photo
- Gerhard Kahr
In South Tyrol, northern Italy, the Bronzolo Bypass Tunnel is the final step in a decades-long project to divert heavy traffic from the SS12 “Brennerstaatsstraße” (one of Italy’s most historically significant north–south corridors) in the section south of Bolzano, between San Giacomo and Bronzolo. Once completed, it will bring lasting relief to the community of Bronzolo.
Bronzolo Bypass Tunnel
- Location
- Bronzolo (South Tyrol), Italy
Building beneath a busy landscape
The new 702-meter tunnel, awarded to the STRABAG AG – Erdbau Srl joint venture in 2023, passes directly beneath residential areas and the Aldino river. This alignment, while vital for traffic relief, comes with complex geological challenges. The ground consists of highly permeable alluvial sediments, glacial moraine, gravel, and debris flow material with low stability.
To manage these conditions, the project team selected the New Austrian Tunnelling Method (NATM) with sequential excavation under the protection of a pipe umbrella system. Each advance section is stabilized with shotcrete, steel lattice girders, and systematic anchoring, supported by extensive jet grouting along the alignment.
“The AT - Pipe Umbrella System allows our miners to advance the excavation safely and efficiently.”
Reliable solutions for loose ground
Sandvik Ground Support plays a key role in ensuring safety and progress under these conditions. The team supplied its proven AT – Pipe Umbrella System and DSI Hollow Bar anchors for primary support.
Using a Sandvik DT921i drilling jumbo with integrated automation and hydraulic pressing units, between 53 and 60 AT 139 steel pipes (each 15–18 meters long) are installed per section to form a pre-support canopy. This setup enables the excavation of 9–10 meters beneath each umbrella. Additional R32 and R51 self-drilling anchors reinforce the tunnel face and shell.
Despite encountering boulders of up to four cubic meters, excavation remains on schedule — a strong indicator of the system’s adaptability in loose ground.
Because of the tunnel’s shallow overburden, continuous geotechnical monitoring is essential. Manual and automatic total stations, inclinometers, and seismic sensors track ground movement to ensure that surface settlements remain within safe limits.
A sustainable connection
The Bronzolo bypass, co-financed by the Autonomous Province of Bolzano and the Fund for Development and Cohesion (FSC), will soon complete a 9-kilometer corridor designed to improve traffic flow and quality of life across South Tyrol’s Adige Valley.
By combining proven excavation techniques with Sandvik’s precision ground support, the project showcases how innovative engineering can deliver lasting infrastructure — even in the most challenging geological conditions.
With Sandvik’s AT Pipe Umbrella System, DSI Hollow Bar anchors, and continuous on-site technical support, the Bronzolo Bypass Tunnel project is progressing safely and on schedule despite challenging ground conditions.
Bronzolo Bypass Tunnel project
Purpose: Final phase of the SS12 relief route to reduce traffic and environmental impact in Laives, Steinmannwald, and Bronzolo.
Tunnel length: 702 m (642 m conventional excavation + 60 m cut-and-cover)
Ground conditions: Loose alluvial sediments, moraine, gravel, debris flow deposits
Support system: 2 x AT pipe umbrella automation systems
Equipment: Sandvik DT921i drilling jumbo with automation and hydraulic pressing units
Products: AT 139 steel pipes, squeezing unit, R32-280 and R51-660 self-drilling hollow bar bolts
Project status: Ongoing – completion expected on schedule
