Slice Data & Diagnostics
Inspect per-slice forces and diagnostics for a surface.
Inspect per-slice forces and diagnostics for a surface.
The slice data modal reports the full set of forces, stresses, and strength terms the solver computed for any individual slice of the critical surface. It is the primary tool for diagnosing a suspicious result — checking where strength is mobilized, where pore pressures are high, and whether the method of slices is behaving near the base of the surface.
Opening slice data
With results displayed and Show Slices on:
- Make sure the critical slip surface is shown.
- Click a slice of the surface on the canvas.
The slice data modal opens, titled with the slice number, the total slice count, and the surface factor of safety (for example, Slice 7 of 30 - FOS 1.24). Click an adjacent slice to inspect it instead.
What the modal reports
The modal lists every diagnostic for the selected slice as a label/value table. Key quantities include:
| Quantity | Unit | Description |
|---|---|---|
| Factor of Safety | — | Surface factor of safety. |
| Angle of Slice Base | deg | Inclination of the slice base. |
| Slice Width / Base Length | m | Geometry of the slice. |
| Slice Weight | kN | Self-weight of the slice. |
| Base Normal Force / Base Normal Stress | kN / kPa | Total normal at the base. |
| Effective Normal Stress | kPa | Normal stress less pore pressure. |
| Shear Strength | kPa | Available shear strength at the base. |
| Shear Stress | kPa | Mobilized shear stress at the base. |
| Pore Pressure | kPa | Pore-water pressure at the base. |
| Matric Suction | kPa | Negative pore pressure (unsaturated zone). |
| Interslice forces | kN | Left/right normal, shear, and resultant forces. |
| M-Alpha | — | The method-of-slices base term (see below). |
Method- and material-specific rows are added when relevant — for example FEA normal and mobilized shear stress, Generalized Anisotropic mapping details, and Generalized Hoek–Brown parameters.
What to look for
- Tension zones. Watch for a base normal force or effective normal stress that goes negative, usually at the toe or crest. This indicates the slice base is in tension, which is non-physical and can distort the result. Consider a tension crack or the tension-handling analysis options.
- M-Alpha problems. For methods that satisfy moment equilibrium (such as Bishop and GLE), the M-Alpha term appears in the denominator of the normal-force equation. When it approaches zero — typically on steeply inclined bases combined with a low factor of safety — the slice normal force becomes ill-conditioned. The solver can reject surfaces whose minimum M-Alpha falls below a configured threshold; a slice with a very small M-Alpha is the one to examine.
- High pore pressure. Compare pore pressure against base normal stress. Where they are close, effective stress and therefore frictional strength is small.