What does the angle of internal friction (φ) specifically signify about a soil's resistance to shear failure?

The angle of internal friction (φ) specifically signifies the frictional resistance that a soil offers against shear failure. Shear failure occurs when the applied shear stress, which is a force acting parallel to a surface, exceeds the soil's internal resistance, causing it to deform excessively or collapse. The angle φ quantifies the contribution of friction and interlocking between soil particles to this resistance. Essentially, it represents how much internal fric....