Which soil grouping is least likely to present embankment and settlement problems?

• A. Gravels, sand
• B. Gravels, sand, organic silts
• C. Plastic silts, clays
• D. Organic soils, clay

Answer: (A)

Gravels and sand are characterized by their granular structure, which provides excellent drainage properties and compaction capabilities. This grouping is typically well-draining, meaning that water can easily pass through, reducing the risk of pore water pressure build-up that often leads to settlement issues. The cohesionless nature of gravels and sands means that they don't retain water like more cohesive soils do, minimizing the risk of expansive or shrink-swell behaviors, which are contributing factors to embankment instability.

Additionally, gravels and sands generally have a higher shear strength compared to finer, cohesive soils. This strength helps to support structures built on them without significant movement or settlement over time. When constructing embankments, these soils can be compacted effectively to achieve desired densities, resulting in stable support for structures such as roads and bridges.

Conversely, the other soil groups mentioned tend to have characteristics like higher plasticity and susceptibility to deformation under loads and moisture changes. Organic silts and clays can compress and settle significantly, while the presence of organic material introduces variability and reduces the soil's overall stability. This makes gravels and sands the ideal choice when aiming to avoid embankment and settlement problems in construction.