The Experimental Estimation of The Elastic Modulus of a Fly Ash Based Trackbed Layer Under Cyclic Loading

Abstract

In a railway track structure system, trackbed layers are designed to compensate for insufficient bearing capacity and/or water or
frost resistance of natural soil. These, so called, ‘capping layers’ can be constructed from raw materials like sand or gravel or from
industrial materials like asphalt or concrete. However, more environmentally and cost friendly alternatives have been studied in recent
years. Fly-ash represents one such promising material and a trial section of a main line track with the capping layer made from
a fly-ash-based mixture was constructed in Czech Republic in 2005. The performance of the capping layer in the section has been
measured since. In this paper, results of the laboratory estimation of the elastic modulus under cyclic traffic-like induced loading are
presented for the most recent group of samples. The results show that the elastic limit of the fly-ash-based material lies well above
the stresses induced by railway traffic and that its behaviour is stable under the cyclic loading. This suggests that the mechanical
properties of the material may not be determinative for the design of the layer and that the feasibility factors may take precedent.
This in turn suggests that either the design strength of the material or the designed thickness of the layer may be possibly reduced.