Which term describes the maximum stable slope angle of a material before it slides?

Which term describes the maximum stable slope angle of a material before it slides?

• A. Angle of repose.
• B. Slope limit.
• C. Critical grade.
• D. Grade line.

Answer: (A)

The angle of repose is the maximum stable slope angle of a material before it slides. It represents the steepest surface slope at which a pile of granular material can remain in balance, because gravity tries to pull grains downslope while friction and interlocking between particles resist that movement. If the slope becomes steeper than this angle, the shear stress exceeds the material’s strength and the material will flow or avalanche until the slope relaxes to the angle of repose. This concept helps in earthmoving because it defines safe stockpile and trench-wall slopes for a given material. The angle of repose varies with material properties and conditions—dry, coarse grains often allow a steeper angle, while moisture and cohesion can change the value. Other terms like slope limit, critical grade, or grade line aren’t the standard way to describe this stability limit.

The angle of repose is the maximum stable slope angle of a material before it slides. It represents the steepest surface slope at which a pile of granular material can remain in balance, because gravity tries to pull grains downslope while friction and interlocking between particles resist that movement. If the slope becomes steeper than this angle, the shear stress exceeds the material’s strength and the material will flow or avalanche until the slope relaxes to the angle of repose. This concept helps in earthmoving because it defines safe stockpile and trench-wall slopes for a given material. The angle of repose varies with material properties and conditions—dry, coarse grains often allow a steeper angle, while moisture and cohesion can change the value. Other terms like slope limit, critical grade, or grade line aren’t the standard way to describe this stability limit.