What phenomenon occurs in saturated cohesionless soil, reducing effective shear strength to negligible values?

In saturated cohesionless soils, the phenomenon that leads to a significant reduction in effective shear strength is known as liquefaction. This occurs when these soils, typically granular in nature and lacking cohesion, lose their strength and stiffness due to an increase in pore water pressure, often triggered by seismic activity or other dynamic loading conditions.

During liquefaction, the soil behaves more like a liquid than a solid. The voids between the soil particles fill with water, increasing pore pressure to a point where the effective stress—the stress that contributes to the soil's strength—drops to almost zero. As a result, the soil can no longer effectively support loads, leading to severe structural issues and instability.

Understanding liquefaction is critical for civil engineering and geotechnical disciplines, especially in areas that are prone to earthquakes or heavy vibrational forces. It underscores the importance of site assessment and the necessity of implementing appropriate engineering controls and mitigation strategies in construction projects.

Consolidation, while related to soil behavior under load, refers to the process where soil volume decreases due to the expulsion of water from the voids over time, which is distinct from the immediate effects observed during liquefaction. Settling refers to the gradual sinking of the ground surface due to various factors