Factor of Safety in Absence of Flow Net Calculator

Factor of Safety Formula:

\[ FS = \frac{(c' \times L') + (\Sigma N \times \tan(\phi'))}{\Sigma T} \]

Effective Cohesion (c'):

kPa

Length of Slip Arc (L'):

Sum of Normal Components (ΣN):

Effective Angle of Internal Friction (φ'):

Sum of Tangential Components (ΣT):

Factor of Safety (FS):

1. What is Factor of Safety in Absence of Flow Net?

Definition: This calculator determines the stability of slopes by calculating the ratio of resisting forces to driving forces without considering pore water pressure effects.

Purpose: It helps geotechnical engineers assess slope stability when detailed flow net analysis isn't available or necessary.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ FS = \frac{(c' \times L') + (\Sigma N \times \tan(\phi'))}{\Sigma T} \]

Where:

\( FS \) — Factor of Safety
\( c' \) — Effective cohesion (kPa)
\( L' \) — Length of slip arc (m)
\( \Sigma N \) — Sum of normal components (kN)
\( \phi' \) — Effective angle of internal friction (°)
\( \Sigma T \) — Sum of tangential components (kN)

Explanation: The numerator represents resisting forces (cohesion + friction), while the denominator represents driving forces.

3. Importance of Factor of Safety Calculation

Details: A FS > 1 indicates stable slope, while FS ≤ 1 suggests potential failure. Typical design values range from 1.3 to 1.5 for slopes.

4. Using the Calculator

Tips: Enter all required parameters. Note that friction angle and tangential components have ±5% uncertainty. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: When is this simplified method appropriate?
A: For preliminary analysis or when pore water pressure effects are negligible compared to other factors.

Q2: What's a typical effective friction angle for soils?
A: 25°-35° for sands, 15°-25° for silts, 10°-20° for clays (with ±5% variation).

Q3: How do I determine the slip arc length?
A: Estimate from cross-section drawings or use trial circular failure surfaces.

Q4: What if I have pore water pressure data?
A: Use more advanced methods that incorporate pore pressure coefficients.

Q5: Why the ±5% notation?
A: These parameters typically have higher uncertainty in field conditions.