Cutting Cutting sideslope Basal reinforced embankments spanning voids: sideslope Diameter 1.7 m to 3 m Roadway embankment, Bad Wünnenberg Bypass, depending on embankment height North Rhine-Westphalia, Germany Road pavement Road pavement ® Geolon PET800 geotextile reinforcement Min. 1.1 m 20 m 1.5 m diameter Chalk karst stratum Void Cross section through the cutting section of the road structure compacted until the level for the pavement subgrade was achieved. Finally, the roadway pavements were constructed on top. Client: Landesbetrieb Strassenbau Nordrhein County, Germany. Consultant: Dr Spang GmbH, Witten, Germany. Compacting embankment fi ll Bad Wünnenberg is a town in the thus maintaining the road in a The required basal reinforcement Contractor: Amand GmbH & Co. KG, state of North Rhine-Westphalia, serviceable condition. properties were determined in Germany. Germany. It is situated on the river accordance with EBGEO (2011). This Aabach, approximately 20 km south of Along the planned route of the road resulted in a design tensile strength of EBGEO (2011) Recommendations for Paderborn. The new section of the road bypass its alignment changes from at least 300 kN/m over a 100 year design design and analysis of earth structures B480n links to the Aftetal bridge, an 800 cuttings to embankment fi lls up to 7 m life at the required strain levels. Geolon® using geosynthetic reinforcements, m long steel composite structure, which in height. In the cuttings where most PET800 geotextile reinforcement, Wilhelm Ernst and Sohn, Germany. spans the Afte Valley at a height of subsidence problems are expected to with an initial tensile strength of 800 almost 70 m and is the central feature of occur fi ll heights of 1.1 m were used. kN/m, fulfi lled the long term design the Bad Wünnenberg bypass. requirements and was subsequently Based on the results of the ground used for the basal reinforcement. To withstand high traffi c loads, Federal survey and geotechnical analysis, it German roads require good quality was found that initial void diameters The subgrade surface was fi rst foundations. This requirement was not of 1.5 m could be expected in the prepared by smoothing and compacting achieved on a section of the B480n fi ssured foundation stratum beneath the the ground surface. Next the layer Bad Wünnenberg Bypass between roadway alignment. These voids would of Geolon® PET800 geotextile the Rhenish Slate Mountains and the result in potential vertical subsidence reinforcement was installed in the Münsterländer Chalk Basin, where the beneath the earth fi lls. direction along the length of the B480n passes over a wide chalk karst roadway. On top of the geotextile area. The underground cavities can In the cutting sections where 1.1 m of reinforcement granular fi ll material, rise to the ground surface, especially in earth fi ll was used an analysis using the having good dilatancy properties, cuttings, resulting in local deformations RAFAEL subsidence method showed was placed and compacted. Further and subsidence. that the expected subsidence diameter lifts of granular fi ll were placed and at pavement surface would be 1.7 Since ground subsidence could not m. In the embankment sections the be completely ruled out along the same analysis showed the expected planned route, the application of basal subsidence diameter at pavement geotextile reinforcement was applied surface to range up to 3 m depending as a form of insurance against possible on embankment height. The resulting future subsidence. If foundation voids maximum allowable geotextile were to arise in the future beneath reinforcement strains ranged from 2% to the road structure then the geotextile 6% depending on the height of earth fi ll reinforcement would be required to on the basal geotextile reinforcement. span across any formed depressions Site preparation works Placing and compacting granular fi ll over Geolon® PET800 geotextile reinforcement 38 39.