Geodynamic Modelling of Geogrid-Stabilised Aggregate on Soft Ground in High Speed Rail Environments Using Field-Derived Shear Wave Data.

Abstract Geogrids have been used for many years to stabilise and enhance the performance of rail ballast and sub-ballast in terms of maintaining both vertical and lateral track alignment. However, the ability of geogrids to improve these properties within a high-speed rail environment at close-to-critical velocity remain uncertain. The potential for geogrid to improve the stiffness and the ability of a geogrid-stabilised aggregate layer to transmit ground waves such as Rayleigh waves has great potential for reducing dig out depth in soft ground in cuttings and reduce the need to use great thicknesses of engineered, high quality aggregate in embankments in order to mitigate the effects of such waves. New research has been conducted on a trial embankment comparing 4 geogrid-stabilised trial sections with a control section. This embankment has been subjected to low strain stiffness testing using geophysical methods to determine if the stabilised sections can offer an increase in ground wave velocity over the control and thereby offer the potential to reduce engineered construction thickness beneath the track on high-speed rail lines. Initial geodynamic modelling using the results of the on-site testing suggests that specific geogrids have a significant potential to reduce overall construction costs by reducing the need to dig-out-and-replace in soft ground in order to mitigate the effects of Rayleigh waves.