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Scientific Reviewed Papers
Russo, Luis Eduardo

Road ramps reinforced with geosynthetics in substitution of a traditional design solution

Abstract

The original design of the state road S.S. n° 500 of Lonigo, located in north Italy, included reinforced concrete retaining walls for the approaching ramps to a bridge, due to problems of land availability. The walls, standing at both sides of the ramps, should have been founded on piles rested on deep sandy layers, due to the poor geotechnical characteristics of the superficial soil. This expensive solution would have required a long construction time not compatible with scheduled completion of the road. As a variation to the original design, an alternative solution has been proposed by replacing the concrete walls with an embankment reinforced along the side with PET woven geogrids to support the steep slopes and, at the base, with two layers of a high strength woven geotextile crossing completely the cross section.

Conclusion

The choice of embankments reinforced along the side with geogrids to support the steep slopes, as alternative solution to the original design of concrete walls and piles, resulted in a significant cost saving of approximately 35-40% of the project budget and also in a time saving. Moreover, three years after completion, the road surface is still perfectly straight, and no sign of relative settlements are evident, demonstrating the reliability of embankments reinforced with geosynthetics on soft cohesive soils. Although a good vegetation cover on the wall faces has been reached in this case, in general it is suggested to keep the slopes up to 70° if no detailed information about the bio-climatic situation is available during the design phase. In conclusion, it has been possible to avoid the execution of the piles under the retaining concrete walls and this alternative solution significantly reduced the final cost, the duration of the works and allowed to carry out the construction with low environmental impact. Although a good vegetation cover on the wall faces has been reached in this case, in general it is suggested to keep the slopes up to 70° if no detailed information about the bio-climatic situation is available during the design phase. In conclusion, it has been possible to avoid the execution of the piles under the retaining concrete walls and this alternative solution significantly reduced the final cost, the duration of the works and allowed to carry out the construction with low environmental impact.