Assessment of strength of individual ballast aggregate by conducting point load test and establishment of classification method

Abstract

Railway ballast course is comprised of crushed coarse aggregate in which the strength of individual particles plays an important function against degradation. Conventionally, the utilized rock material is classified based on the strength of parent rock by implementing uniaxial compressive strength test on prepared rock cores. Present study extends a modified approach to assess and to classify the strength of individual ballast aggregate by conducting point load test (PLT) on hexagon-shaped crushed aggregate gathered from different quarries. Likewise, the testing procedure is carried out on rock cores derived from parent rock to further assess the authenticity of extended classification method. Hence, the concentrated load is diametrically applied on rock core and the PLT is carried out on the hexagon-shaped ballast aggregate positioned in most stable condition. Obtained results reveal that the strength of hexagonal-shaped particles is more than the strength of cylindrical cores. As expected, larger-sized aggregate shows lower point load strength index. Hence, the correction factor considering the size effect is modified for cubic-shaped aggregate. Furthermore, the applied classification method can effectively classify the crushed aggregate based on the results of point load test conducted on individual crushed aggregate. Indeed, the prediction accuracy of classification approach is acceptable.