1. What is Stability Number?

Definition: Stability Number is a parameter used to assess the stability of slopes, particularly in soil mechanics and geotechnical analyses.

Purpose: It helps engineers evaluate slope stability and determine the safety factor against potential failures.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Sn \) — Stability Number (dimensionless)
• \( c \) — Cohesion of Soil (kPa)
• \( Fc \) — Factor of Safety with respect to Cohesion (±5%)
• \( \gamma \) — Unit Weight of Soil (kN/m³)
• \( H_{Mobilised} \) — Depth at Mobilized Cohesion (m)

Explanation: The cohesion is divided by the product of safety factor, unit weight, and mobilized depth to determine the stability number.

3. Importance of Stability Number

Details: Proper stability analysis ensures safe slope designs, prevents landslides, and maintains structural integrity in geotechnical projects.

4. Using the Calculator

Tips: Enter the soil cohesion, safety factor (default 1.9 ±5%), unit weight (default 18 kN/m³), and mobilized depth (default 0.04 m). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for Stability Number?
A: Values typically range from 0.01 to 0.3, with lower values indicating more stable conditions.

Q2: Why is the Factor of Safety ±5%?
A: This accounts for variability in field conditions and measurement uncertainties.

Q3: How do I determine soil cohesion?
A: Cohesion is determined through laboratory tests like direct shear or triaxial tests on soil samples.

Q4: What affects the mobilized depth?
A: It depends on slope geometry, soil properties, and groundwater conditions.

Q5: When is this calculation most important?
A: Critical for designing embankments, excavations, retaining walls, and natural slope assessments.

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