1. What is Angle of Internal Friction?

Definition: The angle of internal friction (φ) is a measure of a material's shear strength, representing the angle between the normal force and resultant force when the material begins to fail.

Purpose: It's crucial in geotechnical engineering for analyzing soil stability, slope failures, and foundation design.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \phi \) — Angle of internal friction (degrees)
• \( \mu \) — Coefficient of internal friction (dimensionless)

Explanation: The arctangent function converts the friction coefficient to an angle in radians, which is then converted to degrees.

3. Importance of Angle of Internal Friction

Details: This parameter helps determine:

• Slope stability and maximum safe angles
• Bearing capacity of soils
• Lateral earth pressures on retaining structures
• Shear strength of granular materials

4. Using the Calculator

Tips: Enter the coefficient of internal friction (μ). Typical values:

• Loose sand: 0.4-0.5
• Dense sand: 0.6-0.75
• Gravel: 0.7-0.9
• Crushed rock: 0.8-1.0

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between μ and φ?
A: μ is the coefficient (ratio), while φ is the angle (degrees) that represents the same friction property.

Q2: How is μ determined experimentally?
A: Through direct shear tests or triaxial compression tests in a geotechnical lab.

Q3: Does this apply to cohesive soils?
A: For cohesive soils (clays), you must also consider cohesion (c) in addition to φ.

Q4: What's a typical angle for construction materials?
A: Common ranges: Sand 25-35°, Gravel 30-40°, Crushed stone 35-45°.

Q5: Why is this important for concrete work?
A: It affects formwork pressures, aggregate interlock, and foundation stability.