Geobag & Geotextile Tube Design Calculator – Pilarczyk Method for River Bank Protection

Geobag & Geotextile Tube Design Calculator

Pilarczyk (1995) / USACE method · Wave + current stability · 2D stacking profile · PDF report

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📐 1. Geobag & Geotextile Tube Design – Why It Matters

Geobags (sand-filled geotextile bags) are widely used for river bank protection, dike reinforcement, and coastal structures. The Pilarczyk (1995) method provides a robust stability formula considering wave height, current velocity, bag density, slope angle, and stacking configuration. This calculator implements both Pilarczyk and simplified USACE approaches.

Pilarczyk stability criterion: Dₚ ≥ (H_s / (Δ * Ψ)) * (K_s * S_k / C_h)
USACE force balance weight: W_req = (F_drag * SF) / (μ * g * cos(α) - sin(α))

🚀 2. Live Geobag Design Calculator

Significant wave height (H_s) m

Current velocity (U_c) m/s

Water depth (h) m

Bank slope angle (α) deg

Bag material specific gravity (ρ_bag)

Number of stacked layers (n)

Safety factor (SF)

MethodPilarczyk (1995)USACE Force Balance

Batch CSV Upload

✅ Expected headers: Hs, Uc, depth, slope, bagSg, layers

Get PDF Report via Email

CSV Template

📊 2D Geobag Stacking Profile

📊 Bag Weight Assessment

📈 Required Weight Trend & Run History

📂 3. How to Use the Calculator

1. Enter hydraulic conditions: wave height, current velocity, water depth.
2. Enter bank geometry: slope angle (degrees). Steeper slopes require heavier bags.
3. Enter bag material properties: specific gravity (typical 1.5–1.7 for sand-filled bags).
4. Set number of stacked layers and safety factor.
5. Select method – Pilarczyk (more accurate) or USACE simplified.
6. Compute: Click "Compute Bag Spec" – required bag weight and stability status appear.
7. 2D profile shows bag stacking on the slope with wave/current forces.
8. Batch CSV: Upload multiple designs for bulk analysis.
9. PDF Report: Download a detailed report with the profile image.
10. History: All calculations saved locally; export or clear anytime.

📈 4. Real‑World Example

Padma River bank protection, Bangladesh
Hs=1.2 m, Uc=1.0 m/s, depth=4 m, slope=20°, bag SG=1.6, 2 layers, SF=1.2.
Pilarczyk method: required bag weight ≈ 85 kg. Commercial geobags (100 kg) are adequate.
The calculator will draw stacking layers and recommend bag size.

❓ Frequently Asked Questions

❓ What is the typical geobag weight?

Common structural engineering sizes are 50 kg, 100 kg, 150 kg, 200 kg, and 250 kg. Our engineering tool suggests the analytical minimum weight; you should select the nearest larger standard commercial production bag weight.

❓ How many layers are needed?

For river banks, 1–3 layers are standard. Stouter structures under heavy current or severe wave impacts use cross-stacked layers. The calculator counts layers to optimize spatial layout resistance factors.

❓ What is the difference between Pilarczyk and USACE methods?

Pilarczyk uses a characteristic structural sizing criteria influenced by relative density and turbulence upgrade profiles. The USACE method maps hydrodynamic fluid-drag profiles acting on geometric structural faces, reduced along steep structural planes.

🌐 Industry Standards & References

Pilarczyk (1995) – Book | USACE EM 1110-2-1601 | CIRIA – Geotextile Design | IGS – Geobag Guidelines

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© ERH Geobag Design Calculator – Based on Pilarczyk (1995) and USACE methods. For structural preliminary engineering.