Numerical modeling of behavior of railway ballasted structure with geocell confinement

Railroad foundations are geotechnical structures that are highly dependent on quality ballast to dampen impact loading and railway vibration, facilitate easy construction, distribute stresses more evenly, reduce long-term settlements and provide a competent base under low confining pressures. However, there are various instances where the use of ballast alone may not be completely adequate or could be prohibitively expensive, i.e. costly transport of select materials, weak subgrade, etc. One possible method of managing these issues is the use of geosynthetics, primarily reinforcements that utilize a confining mechanism to enhance the strength of a soil by utilizing its own internal friction: a mechanism where geocell is applicable. Based on prior large-scale laboratory tests of ballast embankments with geocell confinement and relevant numerical modeling, an acceptable material model was validated for a parametric study using finite element analysis. The purpose of the parametric study is to investigate the effects of geocell confinement on ballasted embankments when encountering a soft subgrade, weaker ballast, or varying reinforcement stiffnesses. This analysis suggests that based on numerical modeling, geocell confinement can have a significant benefit when used on a wide range of subgrade stiffnesses, when using weaker ballast and that mechanically, most polymeric materials commonly used for geosynthetic reinforcements are adequate. The composite effect of the confined ballast selected as infill also demonstrates a “mattressing” effect, distributing stresses more uniformly to the subgrade, which can provide higher bearing capacities and possibly less settlement, all while preventing significant lateral spreading. In certain situations, the benefits provided by behavior of the geocell-ballast composite may be economical by allowing for use of weaker/inferior ballast, less embankment maintenance upon problem soils, improved bearing capacity and reduced foundation settlement.