Queensland Rail Yaamba

Queensland Rail had a fixed 96-hour window to replace 4km of subgrade under an ageing track formation. This train line is the primary industry rail route to Rockhampton, so time was of the essence. Subgrade CBR is as low as 1%, with CBR swells up to 9%.

The original design consisted of a three-layer structure with welded geogrids and geocomposites, and the final two-layer Tensar InterAx geogrid configuration was refined using a combination of an allowable bearing capacity approach (AREMA method) using the Rail Sub-ballast Stabilisation module in Tensar+ software and 2D finite element modelling to ensure that predicted deflections were within tolerablelimits under axle loads of at least 20t.