Foundation and geometry¶
The Type and geometry card defines the shape and placement of the foundation. The section preview, on the right, updates in real time on every change, without consuming credits.
Foundation types¶
| Type | Description | Calculation dimensions |
|---|---|---|
| Strip | Continuous strip footing | B (width), L (length) |
| Pad | Isolated rectangular footing | B × L |
| Raft | Extended slab foundation | B × L |
| Circular | Circular footing | radius R (in calc B = L = 2R) |
The chosen type adapts the shape and depth factors and the section drawing (for strip and pad the column is drawn too; raft and circular are drawn with the excavation).
Geometric parameters¶
| Symbol | Field | Meaning |
|---|---|---|
| B | Base | Foundation width [m] |
| L | Length | Dimension orthogonal to the section [m] |
| H | Height | Thickness/height of the foundation body [m] |
| D | Founding depth | Depth of the bearing plane from ground level [m] |
| R | Radius | Circular footing only [m] |
Embedment height H_F¶
The embedment height H_F defines the effective overburden at the founding
plane. When the foundation is not fully confined by the soil (for example a pad
footing with a working excavation that has not been backfilled), the lateral
surcharge that stabilises the failure mechanism is not γ·D but only γ·H_F.
- Tick « = founding depth » for full embedment: the surcharge is
γ·D(standard behaviour). - Untick it and enter H_F < D for partial embedment: the surcharge reduces
to
γ·H_F, on the safe side.
Effect on bearing capacity
The embedment height acts only on the surcharge term (factor N_q). The depth factors keep using the real depth D.
Analysis condition: drained or undrained¶
- Drained (effective stress): φ′ and c′ are used. This is the typical condition for granular soils and for long-term checks.
- Undrained (total stress): φ = 0 and c = c_u. This is the short-term condition for saturated cohesive soils.
Geotechnical parameters in the failure wedge¶
The Calculation parameters option sets how the values of φ′, c′ and γ used in the formula are obtained:
- Weighted average of the layers — average of the parameters of the layers involved in the failure wedge, weighted on the thicknesses;
- Classic method (bearing layer) — the parameters of the layer the foundation rests on are used.
Comparison with the desktop
When comparing with desktop calculations, make sure this option is set the same way: weighted average and bearing layer can give appreciably different bearing capacities in non-uniform stratigraphies.
Foundation on a slope¶
If the foundation is close to a slope, set the slope inclination β [°] and the foundation–slope distance. The bearing capacity reduces accordingly (reduction factors on the capacity). The section shows the slope on the relevant side.
Convention
In Loadcap NX the slope is drawn on the right of the foundation, with β positive going downhill.
Colour and rendering¶
The foundation colour is customisable and appears both in the 2D preview and in the 3D model.
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