Which type of soil is more likely to be unstable for construction purposes?

The choice of sand as the type of soil more likely to be unstable for construction purposes stems from its properties related to cohesion and stability. Sand particles are generally larger and less cohesive compared to clay particles. This means that when water saturates sandy soil, it can lose structural integrity and become loose, leading to issues like settlement or even major structural failure.

Sandy soils are susceptible to shifting or liquefaction under certain conditions, particularly in seismic events or when subjected to heavy loads. This lack of stability makes them less reliable for supporting heavy structures without adequate engineering solutions such as compaction, drainage, or stabilization techniques.

On the other hand, clay, while potentially problematic due to shrink-swell potential and plasticity, tends to have greater cohesion, which can provide some level of stability when properly managed. Gravel and rock offer much higher stability and load-bearing capacity, making them more suitable for construction purposes compared to sand.