Which field manual test is used to determine the presence of a cohesive clay or silt?

The Pat Test is used to determine the presence of cohesive soils, such as clay and silt, through a practical field assessment. This test involves taking a sample of the soil and manipulating it by patting it in the hand to see how it behaves when pressure is applied. If the sample holds together well after being compressed, it is indicative of a cohesive material.

In contrast to other tests, the Pat Test can be conducted quickly in the field without the need for extensive laboratory equipment, making it accessible for immediate assessment of soil types.

The other testing methods focus on different properties: the Plasticity Test assesses how a soil behaves when it is mixed with water, the Liquid Limit Test determines the moisture content at which a soil changes from a plastic state to a liquid state, and the Unconfined Compression Test measures the compressive strength of soil but is typically used for different purposes rather than simply identifying cohesive materials.