STRESSES AND DEFORMATIONS IN RAILWAY TRACK. VOLUME III

Research carried out during the period May 1977-April 1978 on the behaviour of granular materials and footings used in railway track is reported. The work concentrated on three areas: the investigation of the effects of particle size and grading on the behaviour characteristics of eight ballasts, the determination the optimum spacing-to-breadth ratio for ties using three model footings in sand, and the examination of the theoretical effects on compacted ballast of increasing the axle loadings, using a 37 cm circular footing on sand. This work completes the current project investigating stresses and deformations in railway track. The use of broader gradings, which offers significant improvements in terms of resistance to settlement and increased strength, is recommended. Ballast materials tested are ranked in terms of relative service life and resistance to abrasion. The use of broader ties at the same spacing-to-breadth ratio, which offers a significant improvement in resistance to degradation of track geometry, is recommended. The current (20") spacing appears optimum for the 8" wood ties, given the practical constraints on closer spacing. On the basis of the results obtained from the model circular footing work, it is recommended that the wheel loading on compacted ballast should not be increased without first performing a skin lift to help prevent the development of centrebinding.