Comparison of ballast index tests for railway trackbeds

It is important to have consistent ballast testing methods that provide results reflecting the performance of different ballast materials in the railway trackbed. Extensive laboratory tests have been conducted to investigate the correlation between simple ballast index tests and box tests simulating ballast field loading conditions in a simplified and controlled manner. Ballast is tamped using a vibratory poker, which causes particles to rearrange as the level of the sleeper is raised. The index tests used include single particle crushing tests, oedometer tests, and attrition tests in a revolving drum (WAV, MDA and LAA tests), in addition to water absorption and particle shape characteristics and petrographic analysis. The attrition tests performed in a revolving drum (WAV, LAA and MDA) have been found to give the best correlations with the performance of ballast in the box tests. It is considered that this may be due to the rearrangement of particles in the box test caused by the simulated tamping.