Small grained, less than #200 sieve, platy shaped grains describe which soil type?

Small grained, less than #200 sieve, platy shaped grains describe which soil type?

• A. Non-cohesive
• B. Organic
• C. Cohesive
• D. Gravel

Answer: (C)

Fine-grained soils are the key here. Particles smaller than a #200 sieve are considered fine-grained, and when those grains are plate-like in shape, as clay minerals are, they tend to stick together through electrostatic forces and thin water films. This gives the soil cohesion and plastic behavior, which is the hallmark of cohesive soils. So the description—small grains that are plate-like and clay-rich—best fits cohesive soil. Coarse materials like sands and gravels are non-cohesive, and organic matter or debris isn’t indicated by this plate-like clay description.

Fine-grained soils are the key here. Particles smaller than a #200 sieve are considered fine-grained, and when those grains are plate-like in shape, as clay minerals are, they tend to stick together through electrostatic forces and thin water films. This gives the soil cohesion and plastic behavior, which is the hallmark of cohesive soils. So the description—small grains that are plate-like and clay-rich—best fits cohesive soil. Coarse materials like sands and gravels are non-cohesive, and organic matter or debris isn’t indicated by this plate-like clay description.