A section of ‘Federal Roadway B 180’ at Neckendorf near Eisleben, Germany, is once again in service after being blocked for years. The roadway was destroyed across its entire width in 1987 by a sink-hole. The sink-hole is 30 meters deep and 8 meters in diameter. Although the hole has been refilled, the danger of a new subsidence due to deep underground caverns still exists. In order to put the road into operation again, the sink-hole had to be bridged to ensure acceptably low deflection values of the road base even under heavy truck loads.
Due to lower costs and ‘ductile’ deformation behavior, a geogrid-reinforced gravel cushion was preferred to a concrete bridging plate. A geogrid with very high strength ( UTS = 1200 kN/m ) and high modulus (40 000 kN/m at 3% elongation) was necessary acc. to the design calculations. For this purpose the geogrid was specially produced. The project is the first of its kind using very high-modulus geogrids. The road has been in use since October 1993 without any further deformations.
This paper describes the reinforcement concept, design philosophy, dimensioning, materials used and safety measures (control system) installed, and provides details and photographs of the reconstructed roadway.
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