Damaging of the St. Benedetto Tunnel after the Quake of October 30, 2017: Study and Repair-Paper

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The 30 October 2016 Central Italy earthquake (Mw 6.5) severely damaged the St. Benedetto Pass Tunnel on State Road S.S. 685, forcing the road’s closure. The worst damage occurred over a roughly 25 m section about 920 m from the Norcia entrance: the concrete lining fractured in multiple places, and the road surface rose by about 0.24 m.<br /><br />Investigations by Anas included geological and structural surveys, drilling and sampling, geophysical testing, and laboratory analyses. Results identified a zone of highly disrupted rock around the tunnel and evidence consistent with coseismic fault movement. The precise faulting mechanism remains under study. The damage is attributed to the earthquake’s intensity and proximity, variable rock conditions, and the tunnel’s geometry; shear-related cracking may also have been influenced by the suspended ventilation ceiling.<br /><br />The repair involves removing and rebuilding the damaged lining and associated infrastructure. Work is being carried out in short, supported sections to protect workers and maintain stability. The surrounding cavity is consolidated with fiberglass bolts, followed by construction of a reinforced invert and final lining, waterproofing, drainage, and restoration of the road surface, ventilation, and lighting. Temporary supports were installed during investigations and repair.<br /><br />The case is unusual because direct fault displacement affecting a tunnel is rare. The findings are intended both to restore the tunnel’s safety and to improve understanding of how strong earthquakes and fault movement can damage underground structures.

Keywords

Central Italy earthquake

St. Benedetto Pass Tunnel

State Road S.S. 685

tunnel damage

Norcia entrance

concrete lining fracture

coseismic fault movement

geological surveys

tunnel repair

reinforced invert