Inputs
Optional soil / loading
Results
| # | Course # | Elevation from base | Vertical spacing | Recommended grid length |
|---|
Example data table
| Parameter | Example value | Notes |
|---|---|---|
| Wall height above grade | 2.40 m | Total visible height of wall. |
| Block course height | 0.20 m | Typical modular block rise per course. |
| Embedment depth | 0.15 m | Buried portion below finished grade. |
| Top no-grid zone | 0.40 m | Keep reinforcement away from the top courses. |
| First layer at course # | 2 | Start close to base for stability. |
| Grid every N courses | 2 | Place reinforcement at regular vertical spacing. |
| Grid length factor L/H | 0.70 | Length equals factor times wall height. |
Using these inputs, the schedule places layers at courses 2, 4, 6, 8, 10. With 2.4 m height and 0.4 m top offset, the top grid is course 10. Recommended length is 1.68 m.
Formulas used (simplified)
- Active earth coefficient:
Ka = tan²(45° − φ/2)for level backfill (β≈0). - Grid length:
L = α · H, where0.6 ≤ α ≤ 0.8typical for modular block walls. - Vertical spacing:
sv = n · hcoursewherenis courses between layers. - Layer elevations: from first layer course
c₀then everyncourses up to the last course below the top no‑grid zone. - Count of layers: number of courses flagged as reinforcement within the eligible zone.
- Optional surcharge: additional pressure ≈
q · Ka(not used for schedule, shown for reference).
This tool provides layout guidance only. Final design must follow local codes and manufacturer manuals, with checks for internal/external stability per NCMA/FHWA methods.
How to use
- Select units and enter wall height, course height, embedment, and top no‑grid zone.
- Set the first layer course and the interval (every N courses).
- Choose a length factor; many walls use 0.6–0.8 times height.
- Optionally enter soil parameters if you wish to see derived
Ka. - Review the schedule table and summary cards for total layers and spacing.
- Use “Download CSV” or “Download PDF” to export the results.
- Consult an engineer and manufacturer guidance before construction.
Tip: Increase density of base layers by placing the first few layers every course.
FAQs
Many guides place the first layer at course 1–2 above the base, to intercept higher stresses near the toe. Confirm with your block system requirements.
Spacing of every 2–3 courses is common for many modular block walls, but tall walls often require tighter spacing near the base. Always follow the manufacturer tables.
A length of 0.6–0.8 times the wall height is a typical starting point for preliminary layouts. Site conditions or seismic demands may require longer lengths.
Surcharges increase earth pressures and can change required lengths and spacing in a full design. This tool keeps the schedule logic, but displays the active pressure coefficient.
Terraces and curves introduce complex interactions and minimum spacing between tiers. Use this as conceptual guidance only and consult detailed design resources for multi-tier or curved alignments.
If unknown, default to typical granular backfill values, e.g., φ ≈ 30–34° and γ ≈ 18–20 kN/m³. Confirm with geotechnical data for accurate design.
No. It is a planning tool to discuss concepts and counts. Permit drawings require a stamped design by a qualified professional using manufacturer-specific design methods.