Factor of Safety against Sliding Calculator

Factor of Safety Formula:

\[ FS = \frac{\tan(\phi)}{\tan(I)} \]

Factor of Safety (FS):

FS with Safety Margin (5%):

1. What is Factor of Safety against Sliding?

Definition: The Factor of Safety (FS) against sliding is the ratio of resisting forces to driving forces that could cause slope failure.

Purpose: It evaluates the stability of slopes, retaining walls, and other earth structures to prevent sliding failures.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ FS = \frac{\tan(\phi)}{\tan(I)} \]

Where:

\( FS \) — Factor of Safety against sliding
\( \phi \) — Angle of internal friction of soil (degrees)
\( I \) — Angle of inclination of slope (degrees)

Explanation: The tangent of the soil's friction angle divided by the tangent of the slope angle gives the basic safety factor.

3. Importance of Safety Factor Calculation

Details: Proper FS calculation ensures slope stability, prevents landslides, and maintains structural integrity in geotechnical projects.

4. Using the Calculator

Tips: Enter the soil's friction angle (φ), slope inclination angle (I), and desired safety margin (default 5%). All angles must be between 0-90°.

5. Frequently Asked Questions (FAQ)

Q1: What is a good Factor of Safety value?
A: Typically FS ≥ 1.5 is acceptable, but requirements vary by project and regulations.

Q2: Why include a safety margin?
A: The margin accounts for uncertainties in soil properties, loading conditions, and environmental factors.

Q3: How do I determine the friction angle?
A: Through laboratory tests like direct shear or triaxial tests on soil samples.

Q4: What if my FS is less than 1?
A: FS < 1 indicates potential failure - consider slope flattening, retaining structures, or soil improvement.

Q5: Does this calculator consider cohesion?
A: No, this is the simplified formula for cohesionless soils. For cohesive soils, additional terms are needed.