Belfast sits on the Triassic Sherwood Sandstone, but that bedrock is often buried under 10 to 30 metres of glacial till and soft estuarine clays known locally as sleech. We have logged these deposits on sites from the Titanic Quarter to the Lagan riverfront. Shallow footings rarely work here. When the competent stratum is that deep, we design driven or bored piles that transfer structural loads past the compressible layers. The CPT test is our preferred method for continuous profiling in these soft clays, giving us a clear picture of undrained shear strength before we select pile type and length.
In Belfast till, end-bearing piles on sandstone can mobilise base resistances of 2,500 to 4,000 kPa, but only if the pile toe is properly cleaned and inspected.
