Executive Summary : | Ballast is an important component of the rail track substructure and is responsible for maintaining track alignment, distributing the applied train load to the underlying layers, and providing track drainage. However, the ballast layer when subjected to the repeated passage of trains undergoes vertical and lateral deformations along with the particle breakage. The accumulation of fouling materials like clay and coal fines in ballast impedes its drainage capacity and also reduces its shear strength. The extent of aforementioned track problems increases significantly with the increase in train speed. To avoid any untoward incident from happening, the railways are compelled to carry out frequent maintenance operations that consume huge funds, disrupt traffic and also require the replacement of used and degraded ballast with fresh ballast. Therefore, with a view to enhance the track longevity, the possibility of using rubber coated ballast (RCB) and to reduce the need for quarrying of ballast the use of steel slag (an industrial waste by-product generated during steel manufacturing) as an alternative to conventional ballast will be explored by conducting model track tests. The RCB is anticipated to address the problem of ballast degradation, abrasion and also helps in damping the noise and vibrations. The effect of coal fouling on the performance of conventional ballast/steel slag/rubber coated ballast will also be evaluated. Further, the current project also aims at strengthening the ballasted tracks to support high-speed trains and heavier axle loads by means of (a) geogrid reinforcement, and (b) by combination of geogrid insertions and polyurethane treatment of ballast. The combined use of geogrid at the bottom of ballast layer and the polyurethane treatment of the top portion of ballast will be explored. The geogrid is anticipated to prevent the lateral spreading of ballast near the ballast-subballast interface. On the other hand, the treatment of ballast towards its top with polyurethane will enhance the track stiffness, leads to better load distribution and also prevents the flying of smaller ballast particles due to the effect of high-speed train loading. This method of strengthening ballast can lead to a substantial reduction in the thickness of ballast required for a given allowable train speed or the possibility of allowing high-speed trains for a given ballast thickness. The outputs from the current project will help in formulating the design guidelines that are needed in using RCB and steel slag as an alternative to ballast for sustainable railway infrastructure. |