GEOGRIDS CUT BALLAST SETTLEMENT RATE ON SOFT SUBSTRUCTURES

British Rail Research has found that geogrids are an effective way of reducing the rate of ballast settlement over soft substructures. The main test facility for this work was the rolling load rig at Derby which was used to simulate soft sub-structure conditions and assess the performance of geogrids. The program consisted of three tests in which the track was relaid with or without a geogrid in the ballast layer. Each test involved relaying the track, providing some initial compaction, tamping the track and then monitoring its performance under traffic. The test results indicate that the soft substructure has a detrimental effect on track durability and that installing the geogrid produced a substantial improvement.