PlatformCalc

1. Select the calculation route: the simple spread check or the BR 470-style punching check.
2. Enter the plant or wheel loading, contact dimensions and platform thickness. Confirm load factors and the load-spread geometry.
3. Describe the platform material and subgrade. In BR 470 mode use characteristic undrained strength for cohesive soil, or friction angle and unit weight for granular soil.
4. Enter any geogrid information and check its product properties and placement against the design basis.
5. Run the calculation and review the pressure, punching and stated assumptions. Compare the result with the project ground information and construction requirements.

• The simple route disperses the applied load through the platform using the entered thickness and spread ratio, then compares the resulting pressure with allowable bearing pressure.
• The BR 470-style route adds a simplified punching check using the selected subgrade strength model and clearly stated assumptions.
• CBR, strength and unit weight fields help record ground information; they are not interchangeable design inputs unless the selected method uses them.
• Geogrid strength is reported, but the app does not take a thickness reduction without product-specific design evidence.

This revision keeps the original simple working-platform load-spread check and adds a simplified BR 470-style punching check. The BR 470 mode is intended for independent preliminary checks and transparent reporting of assumptions.

The app does not replace a full geotechnical design, project-specific ground model, settlement assessment, cyclic degradation review, edge stability check, construction quality control assessment or product-specific geosynthetic design.

BR 470 mode uses cu,k for cohesive subgrade, or φ′k and γ for granular subgrade. Allowable bearing pressure is retained for the simple spread fallback.

Simple spread mode checks the dispersed pressure against the entered allowable bearing pressure. CBR, cu, φ′ and γ are recorded for context.

Defaults are φ′platform = 40° and γplatform = 20 kN/m³. Geogrid strength is reported, but no numerical thickness reduction is taken without a product-specific design.

Simple spread mode uses thickness, spread ratio and allowable bearing pressure. Platform γ and φ′ are saved but not required for the simple check.

Use Ctrl+I to insert a row and Ctrl+Y to delete the active row. Selecting Track, Wheel, Strip or Rectangular pad will prefill blank contact dimensions.

BR 470 Case 1 and Case 2 are generated automatically from each included load row and shown in the Results tab/report.

These fixed examples regression-test the calculation engine. They are not project design examples; they are guard rails so later revisions do not silently change core values.

The tests check cohesive BR 470-style punching, granular Nγ interpolation, a deliberate failure case, and the legacy simple spread calculation. Expected values are hard-coded to 3 decimal places.

The report preview is on the right-hand pane. It includes the selected method note, intermediate BR 470 terms and validation warnings.

Choose either the legacy load-spread bearing check or the simplified BR 470 punching check.

Select the subgrade model used by the BR 470 punching check.

Recorded for correlation / context. Not directly used unless you choose to interpret it outside the app.

Characteristic undrained shear strength for cohesive subgrade.

Characteristic effective friction angle for granular subgrade.

Subgrade bulk unit weight used in the granular bearing term.

Fallback bearing pressure used by the simple spread method.

Characteristic friction angle of platform material used in Kp tanδ.

Platform bulk unit weight used in BR 470 punching and retained for legacy data compatibility.

Lower-bound platform thickness; BR 470 mode also checks geogrid cover if selected.

Geogrid is reported and cover is enforced; strength is not used for a product-specific reduction in this simplified mode.

Characteristic tensile strength of geosynthetic reinforcement.

Minimum cover above geogrid. The app enforces at least 0.30 m in BR 470 mode.