Investigation of effect of water content on railway granular supplementary layers

Purpose. To determine the relationship between water content of continuously graded granular supplementary layers for rail­ way substructure and their inner shear resistance and load bearing capacity. Methodology. Four different ‘samples’ were produced as standard granular products from andesite. Two of them are common base courses for road construction in Hungary, the other two are common railway supplementary layers. The author performed laboratory measurements (multi­level shear box tests) that are adequate for the evaluation of inner shear resistance. The measure­ ments of load bearing capacity and Proctor tests were executed in the laboratory of Colas Hungaria Ltd. The author performed measurements with the optimal water content values of each sample, as well as lower and higher values than them. This can show how the given granular material is sensible to the change of water content. Findings. It was proved that the granular supplementary layers, which are standardized products in road construction (as base courses), also seems to be adequate in railway construction; they are not so sensible to the variation of their water content. It does not mean that the other two granular layers are not adequate for railway substructures, but the application of road ‘products’ have to be considered as substitute products. Originality. The author tried to emphasize the adequacy of rock mining for construction of ballasted railway tracks, as well as the optimal use of mineral wealth in every country with its results. Practical value. The obtained results of the present paper can be useful in the area of rock mining, and railway infrastructure engineering. During construction procedures the optimal water content values should be taken into considerations for compaction to be able to reach maximal compactness (density), but too high water content has to be avoided, which is based on the results. They can be also considered in the design phase.