DRILL RIGS AND GROUND SUPPORT | ROCK TUNNELS
BRONZOLO BYPASS TUNNEL, ITALY
Located in the South Tyrol, in northern Italy, the Bronzolo Bypass Tunnel is a key, and also the final, step in a long-term transport improvement initiative to take heavy traffic from the SS12 ‘Brennerstaatsstraße’, an important north-south road link. The approximately 700m-long road tunnel is located south of Bolzano, between San Giacomo and Bronzolo. The bypass is co- financed by the Autonomous Province of Bolzano and the Fund for Development and Cohesion (FSC). Geology along the tunnel alignment comprises loose alluvial sediments, moraine, gravel, debris flow deposits. The alignment passes directly beneath residential areas and the Aldino river. It has complex geological challenges as well as shallow overburden. The majority of the bypass tunnel – 642m – is being
constructed by conventional tunnelling, leaving a short (60m) portion to be built by cut-and-cover method. The contractor is a joint venture of Strabag and Erdbau Srl, which was awarded the package in 2023. To manage these ground conditions, there would be extensive jet grouting along the alignment. The contractor selected to construct the tunnel using the New Austrian Tunnelling Method
(NATM), with sequential excavation under the protection of a pipe umbrella system. Each advance section would be stabilised with shotcrete, steel lattice girders, and systematic anchoring. The contractor used Sandvik Ground Support’s AT – Pipe Umbrella System and DSI Hollow Bar anchors for primary support of the tunnel excavation. A DT921i jumbo with integrated automation and hydraulic pressing units was used to install, per section, between 53–60 @ AT 139 steel pipes (each 15m–18m in length) to form a pre-support canopy. The support arrangement enables the tunnel excavation to proceed 9m–10m beneath each pipe arch. In addition, R32-280 and R51-660 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. For continuous geotechnical monitoring, with the shallow
overburden, both manual and automatic total stations have been employed, and also inclinometers and seismic sensors to track ground movement. Edited report on Bronzolo Bypass, Italy, is based original case study for Sandvik by Andrea Hirling
bolting rigs. The sealed pumpable resin system removes the need for manual chemical handling. Operators can manage the steps, from resin mixing to injection and curing, from inside the cabin. The company has also launched the HPA20 automatic injection pump for underground resin injection, serve rock bolting and anchoring to ground consolidation and stabilisation. The unit can be operated stand-alone or integrated with underground equipment, supported either by onboard hydraulics or an optional auxiliary hydraulic power pack. It can work with Sandvik drill rigs that cannot accommodate onboard bulk resin systems.
Digital Last October, Sandvik launched the DataDrive’31 technology programme as a Euro 80 million (US$93 million) investment to accelerate digital transformation of underground works through data-driven research and product development.
Top left: ARI System.
Bottom left: HPA20 automatic injection pump
Below: Taisei Corporation manages the Shinnozoki Tunnel project, a large mountain tunnel on the border of Yamagata and Akita prefectures in Japan.
Resin systems Further equipment advances introduced recently by Sandvik include fully integrated, end-to-end resin bolting solutions for tunnel support in a single supplier approach. The system unifies its underground drill rigs, pumpable resin systems, resin capsule injection technologies, chemical products and bolt portfolio. The resin bolting portfolio includes pumpable resin
systems for the DD422i/iE Dual Controls development drills and DS412i/iE and DS512i i-series rock bolters, as well as the Automatic Resin Capsules Injection System (ARI) for i-series
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