Around Swindon, we see a lot of projects delayed because the ground report stops at a visual classification. A look at the soil with the naked eye tells you almost nothing about how it drains, compacts, or holds a load over time. The real story is in the gradation curve. Whether you are working on a greenfield site near the A419 expansion, dealing with the stiff overconsolidated clays of the Kimmeridge formation, or screening granular fill from a quarry north of the M4, you need the full particle size distribution picture. A proper sieve analysis combined with a hydrometer test for the fines fraction is how we move from guesswork to defensible design parameters. For sites where the clay content is critical to earthworks specification, the gradation data often feeds directly into a triaxial shear test to nail down the effective stress strength envelope. This avoids the cost spiral of re-engineering after a failed compaction test. The BS 5930 code gives us the framework, but applying it to Swindon's patchwork geology is where local experience counts.
A single particle size curve reveals more about a soil's engineering behaviour than a thousand visual descriptions.
