Large-Scale Triaxial Tests on Railway Embankment Material
SourceLarge-scale vacuum triaxial tests were performed as a part of the European project SUPERTRACK. The triaxial specimen dimensions were large enough to allow testing of large-grained railway ballast material. Two different materials were tested—ballast (two tests) and sub-ballast (one test). The confining pressure used in the triaxial tests was 40 kPa, supplied by a vacuum applied to the inside of the specimen (membrane) and normal atmospheric pressure outside the specimen. The tests thereby had drained conditions throughout. Load-controlled cycling at a frequency of 1 Hz was applied to each specimen. The two tests on ballast material had several cyclic loading stages with different stress amplitudes and numbers of cycles, with one test including more than one million cycles. The specimens were finally loaded to failure monotonically at a displacement rate of 1 mm/min. The parameters and results of these special tests are presented and compared with some results of scaled materials and general functions found in the literature.