Trevi is carrying out the first phases of works to repair the stretch of Arno riverbank in Florence, Italy, which collapsed in May.
The repairs have been earmarked as urgent, before winter weather further damages the 80m stretch of riverbank where the collapse created a 3.5m deep chasm. Staff are working in shifts for what Trevi has described as a “race against time”.
Florence riverbank where the collapse created a 3.5m deep chasm
Works include structural restoration and hydraulic protection. The first works have just been completed which involved the construction of rigid inclusions to strengthen dislodged soil up to 8m below street level, toughening it to create a stable work surface.
Small micropiles were used to insert the rigid inclusion columns, which were 300mm diameter and 7.5m long and made up of a pre-mixed mortar with a C30 strength class.
To lessen impact on nearby structures, the work was performed using dry rotational drilling, with vibrations. The cement grout was applied during the extraction of the drilling rods, so that there was no decompression and the borehole walls were stable.
“We are in the city centre and we want to minimise the impact of works on the citizenship,” said Trevi project director Tommaso Gondolini. “But, at the same time, we must be quick, in order to ensure safety of the riverbank’s protection wall by early November.”
Trevi said it hopes to ensure the safety of the riverbank’s protection wall by early November
A wall will also be built next to the 5m wide masonry tunnel called the Poggi Channel. The wall is to protect and stabilise the tunnel and nearby buildings, but it will also support excavation for a 3.5m deep platform from which further structural works will be carried out.
There will be two walls of 600mm piles situated opposite each other and connected on the top with capping beams and cross beams. Another wall will be constructed next to the old foundation wall that is made out of wooden piles, and a wall for soil support and containment that will be built as part of the road surface restoration. This final wall will be next to the original wall.
The original wall will be repaired with inclined foundation micropiles and cracks will be repaired with grouting and plastering using the cut-and-plug technique.