Erosion Prevention For Lisbon Motorway Embankment

Erosion prevention for Lisbon motorway embankment uses Tensar Geogrid, a cost-effective, rapid solution to prevent erosion from the heterogeneous soil structure of the steep embankments.

The route of the new A10 motorway cuts across mountainous areas between Bucelas and Arruda dos Vinhos and links the A9 circular with the A1 to improve access to Lisbon's northern suburbs.

As a cost-effective, rapid solution to prevent erosion from the heterogeneous soil structure of the steep embankments, Tensar GM4 geogrid was fixed to the face and combined with grass seeded topsoil to provide a vegetative ground cover, which integrated with the existing landscape.

The new motorway is the 7 km first phase of a 40 km connection to Carregado, the A13 and the future new Lisbon airport at Ota.

The phase was completed in September 2003 after 2 years of construction across difficult soils, and included a 100m tunnel and a 1100m viaduct.

The local ground conditions comprise alternate layers of limestone bench and marl.

As the construction required slopes of up to 60deg, the marl layers posed a significant threat of erosion and danger to the motorway.

To prevent this, some 40,000mý of Tensar GM4 geogrid was installed, anchored at the top and bottom of the slopes with aggregate-filled trenches and fixed to the face by pins.

The adjacent rolls of geogrid are overlapped and stitched together with HDPE braid to form secure vertical joints.

The Tensar geogrid was laid over a 10cm layer of topsoil, which was seeded with grass to create a vegetative cover to assist in containing erosion as well as integrating the new motorway construction with the surrounding landscape.

Client: BRISA, Auto-estradas de Portugal Consultant engineer: COBA Motorway construction contractor: ACORIL Empreiterios, S.A.

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