Woven geotextiles span voids on eastern high-speed railway line

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Sarrebourg - France

TenCate Geosynthetics

The use of reinforcement geosynthetics to span voids is a common technique which can be applied to earthworks under sensitive structure like high-speed railway lines. An optimized design according to Eurocode rules and very high-strength products make it possible to bridge relatively large cavities safely in the long term.

In the East of France, on section 42 near Sarrebourg and Phalsbourg, soil subsidence was observed during the preliminary works under the future railways line. At the surface, voids of 3 m were measured where an embankment varying in height up to 10 m was to be built. To prevent the detrimental effects of foundation subsidence and differential deformations propagating up through the embankment fill and impacting the performance of the rail track structure it was decided to install a combination of granular layers and geotextile reinforcement across the base of the embankment.

For the design of the basal reinforced embankment system a void diameter of 3 m was assumed as this was considered representative of the subsidence that would occur. The design analysis was carried out using the RAFAEL method which assumes a cylindrical failure at the sides of the void along with associated soil relaxation. The maximum deflection of the geosynthetic reinforcement under these conditions and then the allowable deformation is a function of the settlement at the ground surface. The RAFAEL analysis showed that the maximum tensile strain in the basal geotextile reinforcement should be limited to < 5% over a 100 years design life to meet the embankment surface deformation limits.

The geotextile reinforcement TenCate Geolon® PET800 (initial tensile strength 800 kN/m) within the granular layer, provided the tensile strength and stiffness to maintain serviceable conditions at the base of the embankment.

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