A Case Study of a 42-m High GRS Retaining Structure and CO₂ Footprint Reduction due to the use of Marginal Backfill Available on site

Retaining walls are necessary structures for a variety of applications in road construction. Especially at locations where the elevation difference is very high or the foundation soil is weak, the construction of reinforced concrete or masonry retaining walls become not only very expensive, but sometimes almost impossible. In the Northern Marmara Motorway Project, Kurtkoy – Akyazi Section, where an elevation difference of 42 m existed, the most feasible solution was a geosynthetic reinforced soil retaining structure. Because the facing of the GRS retaining structure was designed as a geogrid wrap around facing with an inclination of 70^o and geogrid was used as reinforcements, the marginal fill obtained from the tunnel excavation nearby could be used in the reinforced fill. This allowed to significantly reduce the CO₂ emission compared to the case if a select fill material would have been necessary. The CO₂ emission due to the hauling and quarry operations was reduced from 7,630,000 kg to 477,000 kg, in other words by more than an order of magnitude. Additionally, by using the excavated material, further environmental benefits were achieved. The most important of these benefits are avoiding additional quarry operations which also disturb the natural habitat and cause air and noise pollution and also saving from covering natural habitat by depositing the tunnel excavation.