Soil cohesion is the component of shear strength in soil that arises from the molecular attraction and bonding between soil particles. It represents the internal “stickiness” or resistance of soil particles to being pulled apart, independent of the normal stress acting on them. Cohesion is most significant in fine-grained soils such as clays, where electrochemical forces and water films between particles create strong interparticle bonds. In contrast, coarse-grained soils like sands and gravels generally exhibit little or no cohesion. Cohesion plays a role in soil stability, slope design, and foundation engineering, as it affects how soil can resist shear stress before failure occurs. The total shear strength of soil can be expressed by the Mohr-Coulomb equation.
