Which type of soil can have elastic and consolidation settlements occurring simultaneously?

The correct choice identifies sandy soil as the type of soil that can experience both elastic and consolidation settlements at the same time. Elastic settlement occurs as a result of immediate changes in loading, where the soil compresses and then rebounds once the load is removed; this is typically observed in granular soils like sand.

On the other hand, consolidation settlement is a time-dependent process that involves water expulsion from the soil voids when subjected to increased loading, primarily seen in fine-grained soils like clay and silt.

Sandy soils, being granular, are less susceptible to long-term consolidation effects compared to fine-grained soils but do exhibit both immediate elastic deformation and some degree of consolidation due to their limited cohesion and the potential for pore water movement, especially in saturated conditions. This dual response makes sandy soil unique in its settlement behavior compared to other soil types, which either predominantly undergo elastic settlement or long-term consolidation, but not typically both at the same time.

Fine-grained soils, like clay or silt, are generally associated more with consolidation settlements, while sandy soils are recognized for their quicker elastic responses under loading conditions. Therefore, sandy soil is correctly identified as the type that can simultaneously undergo both elastic and consolidation settlements.