Angle of internal friction

The angle of internal friction is a measure of how much resistance a material, like soil or rock, has to sliding or shifting internally when under pressure. Think of it as the material’s "stickiness" or "grip" inside; a higher angle means it can resist larger forces pushing it to move or slide past itself. This property is crucial in engineering for designing stable foundations and slopes, as it helps predict how materials will behave under different stresses and ensures structures remain safe and secure.