What type of soil is most susceptible to liquefaction?

Loose sand is identified as the type of soil most susceptible to liquefaction due to its specific physical and structural properties. Liquefaction refers to the process where saturated soil substantially loses strength and stiffness in response to applied stress, often due to intense shaking during an earthquake.

Loose sand has a particle size and structure that allows for significant pore water pressure to develop when subjected to dynamic loading. When the solid grains are in a loose arrangement, they can easily rearrange during seismic events, resulting in reduced effective stress and a loss of soil strength. This rearrangement, paired with the saturation of the sand, creates a condition that can lead to the soil behaving more like a fluid than a solid, hence the term 'liquefaction.'

In contrast, clay and loamy soils exhibit cohesive properties that generally allow them to maintain stability under stress, while compacted gravel tends to have high densities that resist liquefaction. The granule interlocking in gravel creates a robust framework, making it less susceptible to the quick changes in stress and pore pressure associated with liquefaction phenomena. Therefore, the characteristics of loose sand specifically make it the most vulnerable type of soil in these scenarios.