The alluvial fans that shape Fresno's subsurface come with a mix of sandy loams and silty clays deposited by the Kings River system. Seasonal moisture swings here can push the plasticity index of near-surface soils above 15, which directly impacts the resilient modulus used in pavement modeling. We run the full suite of index and strength tests required for AASHTO 93 structural design: grain size distribution per ASTM D422, Atterberg limits per ASTM D4318, and soaked CBR per ASTM D1883. Every pavement section we configure accounts for the high shrink-swell potential common in east-side expansions near Clovis, where clay lenses can wreak havoc on untreated subgrade. Before finalizing the asphalt layer coefficients, the CBR road subgrade assessment quantifies the support value the soil actually provides, while Proctor tests lock in the compaction target that keeps the base course stable through Fresno's 100-degree summer stretches.
A 1% drop in subgrade compaction below the 95% modified Proctor target can reduce the pavement structural number by 0.12—enough to cut design life in half on a Fresno arterial.
