Portlaoise sits at approximately 140 metres above sea level on a landscape shaped by glacial deposits over Carboniferous limestone. Every new road widening, industrial yard, or residential access road in the town depends on one critical parameter: the bearing capacity of the compacted layer. Our laboratory CBR test provides that exact value under controlled moisture and density conditions, removing the variability that field testing sometimes introduces. For the past five years, earthworks contractors working on the Portlaoise Southern Bypass and local housing schemes have relied on our soaked CBR results to validate their pavement designs. The procedure follows I.S. EN 13286-47, with specimens compacted at optimum moisture content and submerged for 96 hours to replicate the worst groundwater scenario typical of the low-lying areas near the Triogue River. A single CBR figure can mean the difference between a 300 mm capping layer and a 500 mm one, with significant cost implications. When the subgrade shows marginal values, we often recommend complementing the CBR with a SPT drilling campaign to correlate dynamic penetration resistance with the soaked bearing ratio across the site.
A soaked CBR test in our Portlaoise lab compresses four days of worst-case groundwater conditions into a single design parameter that determines every centimetre of pavement thickness.
