The main functions of geotextiles in a railroad subbase are separation and filtration, but in addition also drainage and reinforcement can be of relevance. In order to quantify the influence of geotextile layers, fatigue loading tests were carried out at the University of Dresden/ Germany.
In a big test box (1,4 x 1,1 x 1,0 m) a multilayer system of rubber plate, subgrade, geotextile, sand, ballast stone bed and sleeper was built in, and a cyclic load of maximum 76 kN was applied on top. This device enables almost realistic conditions in a scale of 1:1. The amount of 5 mio. load cycles between 7 and 12 Hz, which simulates 160 km/h speed, corresponds to the annual load of a heavily trafficked railroad track.
As a result the surprisingly high increasing of the Ev2 parameter(= soil stiffness) with time was obtained. Also the strong reduction of settlement showed the positive influence of geotextiles. In summary it is to say, that geotextiles used at fine grained subsoils lead to a strong improvement of the whole railroad system.
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