Slope Stability Calculator – Bishop Simplified Method with 2D Slice Visualization

Slope Stability Calculator – Bishop Simplified Method

2D slice diagram · Pore pressure ratio · Multiple layers · PDF report · Batch CSV · Trend chart

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📐 1. Slope Stability Analysis (Bishop Simplified)

Slope stability is critical for embankments, natural slopes, and excavations. The Bishop simplified method divides the slope into vertical slices and calculates the factor of safety (FoS) by satisfying moment equilibrium. This tool supports up to two soil layers, pore water pressure ratio (r_u), and provides a 2D slice visualisation.

FoS = Σ [c·b + (W – u·b)·tanφ] / Σ [W·sinα]
Where: c = cohesion, φ = friction angle, W = slice weight, u = pore pressure, α = slice base inclination.
The calculator uses a simplified circular failure surface with user‑defined geometry.

🚀 2. Live Slope Stability Calculator

Slope Height (H) m

Slope Angle (β) degrees

Number of Slices (n)5 slices8 slices10 slices

Layer 1: Cohesion c₁ (kPa)

Layer 1: Friction angle φ₁ (deg)

Layer 1: Unit weight γ₁ (kN/m³)

Layer 2: Cohesion c₂ (kPa)

Layer 2: Friction angle φ₂ (deg)

Layer 2: Unit weight γ₂ (kN/m³)

Pore pressure ratio (r_u)

Batch CSV Upload

✅ CSV: H, angle, c1, phi1, gamma1, ru

Get PDF Report via Email

CSV Template

📊 2D Slice Diagram (Circular Failure Surface)

📊 Driving vs Resisting Moments

📈 Factor of Safety Trend & History

📂 3. How to Use the Calculator

1. Enter slope geometry: height (H), slope angle (β).
2. Select number of slices – more slices increase accuracy.
3. Enter soil properties for up to two layers – cohesion, friction angle, unit weight.
4. Set pore pressure ratio (r_u) – typical values 0.2–0.5 for saturated conditions.
5. Compute: Click "Compute FoS" – factor of safety is calculated, and the 2D slice diagram updates.
6. FoS bar shows safety level: green if FoS≥1.5, orange if 1.2–1.5, red if <1.2.
7. Batch CSV: Upload multiple designs for bulk analysis.
8. PDF Report: Download a report with the slice diagram.
9. History: All calculations saved locally; export or clear anytime.

📈 4. Real‑World Example

Embankment slope, Bangladesh
H = 8 m, β = 30°, c = 10 kPa, φ = 25°, γ = 18 kN/m³, r_u = 0.2.
The calculated FoS ≈ 1.35 – marginal. Improve by flattening slope or adding drainage.

❓ Frequently Asked Questions

❓ What is a safe factor of safety?

For permanent slopes, FoS ≥ 1.5 is usually required. For temporary works, FoS ≥ 1.2 may be acceptable.

❓ How does pore pressure affect stability?

Higher pore pressure reduces effective stress, lowering shear strength and FoS. Drainage measures improve stability.

❓ Is the tool free?

Yes, completely free. Batch processing supports up to 100 rows per CSV.

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© ERH Slope Stability Calculator – Bishop simplified method. For preliminary analysis only.