Angle of Internal Friction given Weighted Friction Angle Calculator

Formula:

\[ \phi_{iw} = \frac{\phi_w \times \gamma_{sat}}{\gamma'} \]

Weighted Friction Angle (φw):

Saturated Unit Weight (γ_sat):

kN/m³

Submerged Unit Weight (γ'):

kN/m³

Tolerance:

Internal Friction Angle (φ_iw):

1. What is Angle of Internal Friction given Weighted Friction Angle?

Definition: This calculator determines the internal friction angle of soil considering weighted friction angle, saturated unit weight, and submerged unit weight.

Purpose: It helps geotechnical engineers analyze soil stability and shear strength in various conditions.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \phi_{iw} = \frac{\phi_w \times \gamma_{sat}}{\gamma'} \]

Where:

\( \phi_{iw} \) — Internal friction angle with weighted friction angle (°)
\( \phi_w \) — Weighted friction angle (°)
\( \gamma_{sat} \) — Saturated unit weight (kN/m³)
\( \gamma' \) — Submerged unit weight (kN/m³)

Explanation: The weighted friction angle is multiplied by the saturated unit weight and divided by the submerged unit weight to get the effective internal friction angle.

3. Importance of This Calculation

Details: Accurate determination of internal friction angle is crucial for slope stability analysis, foundation design, and earth pressure calculations.

4. Using the Calculator

Tips:

Enter the weighted friction angle in degrees
Provide saturated and submerged unit weights in kN/m³
Set tolerance percentage (default ±5%)
All values must be positive numbers

5. Frequently Asked Questions (FAQ)

Q1: What is weighted friction angle?
A: It's an effective measure combining materials' friction properties and their relative contributions in geotechnical analysis.

Q2: How do saturated and submerged unit weights differ?
A: Saturated unit weight includes water in all pores, while submerged unit weight considers buoyancy effects when soil is underwater.

Q3: Why include a tolerance percentage?
A: The tolerance accounts for measurement uncertainties and material variability in real-world conditions.

Q4: What are typical values for these parameters?
A: For sand: φw=30-40°, γsat=18-22 kN/m³, γ'=10-12 kN/m³. For clay: φw=15-25°, γsat=16-20 kN/m³, γ'=8-10 kN/m³.

Q5: How does this relate to soil shear strength?
A: Internal friction angle is a key parameter in Mohr-Coulomb failure criterion for determining soil shear strength.