Which field manual test checks for cohesive soil?

The Plasticity Test is used to evaluate the plasticity characteristics of cohesive soil. This test measures the soil's ability to deform without cracking or breaking, which is a crucial property for cohesive soils like clay. It specifically assesses the soil's plastic and liquid limits, providing valuable information on its behavior under varying moisture content.

Cohesive soils, such as clays, can have significant changes in their properties with moisture variations. Understanding their plasticity is essential for construction and engineering projects, as it helps determine how the soil will behave when subjected to load, environmental conditions, or water content changes. The results from the Plasticity Test inform engineers about the soil's suitability for construction purposes and potential challenges, such as shrink-swell behavior.

While the other tests mentioned may assess soil properties, they do not specifically target the cohesive nature of soils or their plastic limits. The Drying Test measures moisture content, but it doesn't directly correlate with the cohesive behavior. The Proctor Test focuses on determining optimum moisture content and maximum density for compaction, which is important but does not evaluate plasticity. The Compaction Test also deals with soil density and moisture content, not specifically assessing cohesive characteristics.