Which factor significantly influences the shear strength of cohesive soils?

Moisture content plays a critical role in influencing the shear strength of cohesive soils, particularly in clay. In cohesive soils, shear strength is derived from both the soil's effective stress and the moisture content present within the soil matrix. As the moisture content increases, the cohesion of the soil decreases due to the reduction in interparticle forces, commonly referred to as suction.

When water fills the voids between soil particles, it affects the effective stress by adding pore water pressure, which counteracts the stress that the soil structure can handle. This leads to a reduction in shear strength. Conversely, as moisture content decreases, cohesive forces between particles become stronger, leading to an increase in shear strength.

Understanding this relationship is vital for engineers when assessing soil behavior, designing foundations, and evaluating potential failure mechanisms in slopes or embankments. Consequently, moisture content is a fundamental consideration in geotechnical engineering when analyzing and predicting the behavior of cohesive soil under various loading conditions.