Road subgrade design in Sydney relies on precise geotechnical investigation using dynamic cone penetrometers and falling weight deflectometers. Our field team operates out of a mobile lab equipped to perform in-situ CBR tests and compaction control across Sydney's diverse terrain, from the Hawkesbury Sandstone ridges to the alluvial flats along the Parramatta River. Before any pavement layer is placed, the subgrade must be tested for bearing capacity and moisture sensitivity. For sites with variable fill or soft clay, we combine the subgrade study with a georradar survey to map buried anomalies, then run plate load tests on compacted layers to verify modulus values directly on site.
Subgrade CBR variability in Sydney's western clay belts can exceed 50% over 50 metres, demanding site-specific testing rather than reliance on regional maps.