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The project is part of the broader work planned for the modernisation and safety management of the current S.S.106 “Jonica” trunk road, on the stretch approximately between 256+000 and 329+000. The project covered a total length of approx. 52 km.
The project was drafted to tackle the critical issues regarding the present configuration of the S.S.106; the width of most of this stretch remains no more than 7.50 m, which is inadequate and unsafe. It also frequently crosses through towns and villages, and is thus affected by long-distance traffic.
The considerations made during the feasibility study regarded three possible solutions. The project solution deriving from the study of the alternatives is solution no. 4, configured as a route variant from the existing S.S. 106, with type B section.
The acoustic impact produced by the new infrastructure was estimated using two different methodological approaches.
The first was the Burgess simulation method, which takes account of parameters characterising vehicular traffic (vehicles per hour, traffic composition) and the distance between noise sources and receptors. It remains less accurate, however, than the second method, which uses the SoundPlan simulation model.
To obtain more accurate results, the barriers were subsequently positioned using the SoundPLAN simulation software (version 8.2).
SoundPlan is an elaborate noise simulation model, based on the Ray Tracing technique, which can be used to simulate the propagation of noise in complex source and orography situations. The calculation model for the road axis is the French method NMPB Routes 96, with a number of rays equal to 100 and a number of reflections equal to 5. The propagation distance has been considered up to 1000 metres. The noise level estimate takes account of traffic composition, number and speed of vehicles, the type of asphalt and the slope of the road. The high quantity of initial information, together with the level of precision set at the data processing stage yields results that are very accurate, although onerous in terms of calculation resources.
The 3D reconstruction of the digital ground model (DGM), carried out by the SoundPlan software, using triangulations, showed the particular complexity of the areas the project route runs through, given their orographical variability from the sea. The 3D project was fully integrated into the existing situation, considering its entire extension, for long stretches, through tunnels and over viaducts.
The settings of the post operam simulation took account of the morphological characteristics of the site, the elevations in the project, the properties of the road surface and the flows relating to the project status.
Horizontal maps at a height of 4 metres were extrapolated from the calculation model for the post operam scenario during the diurnal and night reference periods. The noise mitigation work for the receptors affected by the noise were designed based on the results of the model, and the simulations for the post-mitigation scenario were then conducted during the two reference periods.
Weathering steel and PMMA barriers were envisaged along the flat/raised/dugout stretches, and integrated barriers on the viaduct stretches.
The base module has a length of 3000 mm and a height of 500mm. Modules were stacked to reach the height required for the work envisaged. The last two closing panels were made of PMMA, bringing the barrier up to a height of 3 metres.
The barriers were installed using uprights resting on a foundation of reinforced concrete cast in situ. The upright (also in weathering steel) and the sound-absorbing panel were connected with plastic joints, with the essential task of eliminating the acoustic bridges. The foam rubber adhesive gasket is weather-resistant.
The uprights are flanged at the base so that they can be secured to a dedicated concrete element with a plate and anchor bolts, or with expansion bolts.
The second type of barrier is built-in (bridge edge, class H4) with a height of 3 metres, and installed on a supporting wall.
A maximum overall width of 50 cm is required, with a flexible longitudinal element that can be easily connected to the ANAS barriers.
The barrier must also be equipped with a motorcyclist protection edge, so that an appropriate connecting element can be used to guarantee continuity with the motorcyclist protection devices of the ANAS barriers.
