Which soil type indicates a potential for shrink and swell behavior?

The correct answer is indicated by clay, which is known for its shrink-swell behavior due to its unique properties. Clay particles are very small and have a high surface area relative to their volume. This high surface area allows clay to absorb water effectively. When moisture is added to clay, it swells as the water is absorbed between the particles. Conversely, when the moisture content decreases, clay can shrink as the water is lost, leading to contraction.

This behavior can have significant implications for construction and engineering, as structures built on clay soils can experience movement, which might lead to cracks and other structural issues. In contrast, other soil types like gravel, silt, and sand have different particle sizes and compositions that do not exhibit the same degree of shrink-swell behavior. Gravel particles are generally too large to retain significant water and have minimal change in volume. Silt and sand also lack the necessary clay minerals that contribute to this behavior. Thus, clay is the soil type most commonly associated with potential for shrink and swell.