Basal reinforced embankments on piles: A1/N1 dual carriage

Basal reinforced embankments on piles: A1/N1 dual carriage

A1/N1, Ireland | TenCate Geosynthetics

Challenge
A section of the A1/N1 dual carriageway between Dundalk and Newry, forming the cross border link between the Republic of Ireland and Northern Ireland, has recently been constructed. The project was faced with many challenges, one being the crossing of the Flurry bog, a large peat bog combined with very soft silts of almost 1km in length, with depths ranging up to 9m. Beneath the peat bog was a firm stratum of gravel overlying rock. The area is subject to periodic flooding from the adjacent Salmonoid River, and the area resembles more of a wetland than a bog.

A1/N1, Ireland | TenCate Geosynthetics

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Solution
The final design incorporated TenCate Geolon® PET geotextile reinforcement across the tops of the pile caps. Depending on the embankment height two different geotextile reinforcement combinations were used. In order to gain access to the site, a working platform needed to be constructed. As the foundation soil was very weak, a TenCate Polyfelt® TS80 geotextile/TenCate Miragrid® GX35-35 geogrid stabilisation layer was placed in order to construct a reinforced working platform across the base area of the planned piled embankment. The appropriate TenCate Geolon® PET geotextile reinforcement was then laid out across the top of the pile caps. A comprehensive embankment monitoring program was performed.

Benefit
The basal geotextile reinforcement deforms between the pile caps thereby transferring the un-arched embankment loading onto the pile caps.