What is the relationship between soil density and liquefaction risk?

Lower soil density increases liquefaction risk due to the way soil particles are arranged and behave under stress, particularly during seismic events. When the density of soil is low, there is more space between the particles, making the soil structure more susceptible to shifting and rearranging under conditions such as shaking from an earthquake.

During liquefaction, saturated, loose granular soils can lose their strength and behave like a liquid when subjected to stress. This phenomenon commonly occurs in areas with loose, unconsolidated soils, where the soil particles are not tightly packed. The increased void space allows for easier movement of water within the soil, which can lead to a reduction in effective stress, thus heightening the likelihood of liquefaction occurring.

Soil density is a critical factor because denser soils generally have more contact between particles, thereby improving cohesion and reducing the potential for catastrophic failure during seismic events. In contrast, lower-density soils generally do not have the same structural integrity, leading to a higher risk of devastating liquefaction effects. Understanding these relationships helps engineers and planners to assess and mitigate risks in prone areas effectively.