Use of synthetic inclusions for enhanced behaviour of railway ballast under impact loading

Ballasted rail tracks form one of the largest worldwide networks catering to passenger and freight transportation. However, track deterioration associated with severe dynamic wheel loads is inevitable over the years leading to high maintenance costs. Geosynthetics and energy-absorbing rubber mats have increasingly been applied in rail track foundations to improve track stability and reduce the life-cycle cost of the railway system. This paper presents the results of an experimental study carried out using a high-capacity drop-weight impact testing apparatus to investigate the deformation and degradation response of railway ballast under impact loading conditions. The effectiveness of the geogrid reinforcement in attenuating impact-induced damage and the enhanced ballast performance achieved by the simultaneous use of geogrid and rubber mats are evaluated and discussed. Test results have shown that the use of a biaxial geogrid at the ballast-subballast interface may be an effective way of reducing the ballast deformation and degradation under impact loading. However, the provision of rubber mats at the bottom of the ballast bed and a geogrid layer at 100 mm height was found to be an optimised solution for minimising the ballast permanent strains and the breakage of aggregates upon successive impact blows.