Selection and testing of ballast stones for underground railway tracks

Abstract

Ballast is broken pieces of hard rocks such as sandstones, schist, etc. approximately 25-60 mm size, over which the railway tracks are laid. The function of the ballast is to transfer the applied load over a large surface, provide adequate elasticity, prevent creep and hold the sleepers in position. Also under wet conditions, it would permit free drainage and allow free grade to be obtained. It is reported that a large proportion of serious accidents occur through derailments of carriages. Many such accidents may be due to the poor quality of ballast stones. The paper discusses the essential properties of ballast stones and methodologies for testing these properties.