1. What is Total Normal Force at Base of Slice?

Definition: This calculator determines the total normal force acting at the base of a soil slice, considering effective stress, pore pressure, and arc length.

Purpose: Essential for slope stability analysis using methods like Bishop's simplified method or ordinary method of slices.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( P \) — Total normal force (Newtons)
• \( \sigma' \) — Effective normal stress (Pascals)
• \( \Sigma U \) — Total pore pressure (Newtons)
• \( l \) — Length of arc (meters)

Explanation: The sum of effective stress and pore pressure is multiplied by the length of the slice's base to get the total normal force.

3. Importance of Tolerance Value

Details: The ±5% tolerance (adjustable) accounts for measurement uncertainties and material variability in geotechnical calculations.

4. Using the Calculator

Tips: Enter effective stress in Pa, pore pressure in N, arc length in m, and tolerance percentage. All values must be ≥ 0 except length which must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is effective normal stress?
A: The stress carried by the soil skeleton, calculated as total stress minus pore water pressure.

Q2: Why include pore pressure?
A: Pore pressure reduces the effective stress and thus the shear strength of the soil.

Q3: How is arc length determined?
A: It's the curved length of the failure surface at the base of the soil slice being analyzed.

Q4: When would I adjust the tolerance?
A: Increase for highly variable soils or when input data quality is poor; decrease for controlled lab conditions.

Q5: What units should I use?
A: Consistent SI units are required - Pascals for stress, Newtons for force, meters for length.

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