L’Aquila, July 7, 2021 – A sequence of horn blasts and a series of detonations broke the pre-dawn silence at the mouth of the L’Aquila Basin, in the territory of Lucoli.
Explosions of the microcharges that allowed the controlled demolition of part of the Fornaca Viaduct on the A24 highway, in the direction of L’Aquila. A surgical operation that erased half the viaduct from the landscape in a matter of seconds, allowing the highway to reopen to traffic as early as 7 a.m. this morning, safely in both directions on the opposite carriageway.
The controlled abatement operation, the first of its kind on the A24, is part of the plan for earthquake-proofing the viaducts of the A24 and A25 freeways, which was launched last year by concessionaire Strada dei Parchi with the dismantling and complete reconstruction of the western carriageways of as many as six viaducts. Reconstruction and anti-seismic upgrading works that will continue in the coming months on other viaducts on the section between the Tornimparte and L’Aquila Ovest interchanges, with the aim of making the entire section safe and thus the connection of the city of L’Aquila with the Rome-Pescara route.
The Fornaca viaduct, like its neighbors on the L’Aquila section, is in fact among the first built on the A24-A25 network. Eight pre-stressed concrete spans that touch thirty meters in height and support more than 300 meters of highway seat. In its more than 50 years of service, it has brilliantly passed the test of recent earthquakes, ensuring the arrival of timely relief to affected populations in 2009. Today the time has come to replace it with a new structure of greater durability and strength. “The new Fornaca Viaduct Will retain the layout and conformation of the old but Will be rebuilt with the most advanced engineering criteria and adapting it to the latest seismic building regulations,” says engineer Stefano Ventura, construction manager.
Last night the operation area was evacuated to a radius of 200 meters. The sounding of the horn, in the tradition of the bomb squad, gave the signal to start the domino effect of the microcharges, cleverly placed at the weakening points in the preparatory phase. An insignificant amount of explosives compared to the colossal size, because the structure is weakened and the microcharges induce a twist at special hinge points that facilitates its collapse. Everything has been planned in great detail in recent weeks to ensure maximum control and safety at every stage. “The structure is equipped with instruments to measure the effects induced by the abatement operations and seismographs for monitoring before, during and after the abatement,” explains Eng. Ventura. “Protective devices are also provided to contain any projections of material.” At 5:44 a.m. today, the eastbound carriageway of the Fornaca Viaduct crumpled like a house of cards. Timely checks by safety officials made it possible to reopen the opposite carriageway to vehicle traffic on schedule, after only three hours of traffic closure between L’Aquila Ovest and Tornimparte. Debris from the demolished viaduct will be removed in the coming days.
“It is confirmation of the effectiveness of a method, strongly desired by Strada dei Parchi”, says CEO Riccardo Mollo, “that makes it possible to keep pylon and deck clearance times as short as possible, with instantaneous demolition, and to keep the highway in operation at all times, minimizing inconvenience to our customers. Demolition and reconstruction of the viaduct take place on only one carriageway at a time, while the other remains reserved for vehicle traffic. In this section of the A24 highway, where there is a more urgent need to intervene due to the presence of works built with obsolete anti-seismic criteria and close to the craters of the recent earthquakes, we have also planned a construction site in continuity between the viaducts affected by the reconstruction work. In this way, our customers will be spared the annoying zig-zag between roadways, and we can all proceed, motorists and construction sites, more expeditiously. There will also always be guaranteed lightening segments in the section, where slower vehicles will be allowed to overtake.”
