The Stability module of CiviLab 7.1 has its own ribbon tab, organised in four groups: Bishop method, Spencer / Morgenstern-Price, Non-circular surfaces and Seismic. Each group has its own input window, list of calculations and sheets.
Methods
- Spencer (1967): interslice forces inclined at a constant angle;
- Morgenstern-Price (1965): X = λ·f(x)·E with a half-sine f(x);
- solved with the algorithm of Zhu et al. (2005), F and λ displayed;
- reference method selectable for the search (Bishop, Spencer or Morgenstern-Price); comparison Fellenius / Bishop / Spencer / Morgenstern-Price.
Geometry and soils
- soil layers defined by their top boundary, with γ, γsat, c′ / φ′ (drained) or cu (undrained);
- water table and surcharge at the crest;
- input window with a permanent scaled section and Excel import / export.
Eurocode 7 check
- factor of safety F compared with the required factor;
- NF P 94-270 §10: design approach 3 (A2 + M2 + R3), partial factors of annex C (γQ = 1.3; γφ′ = 1.25; γc′ = 1.25; γcu = 1.4), γR;d = 1.10 (§10.5), inequality 10.2.1 Fd ≥ γR;e·γR;d.
Results
- scaled sheet: layers, water table, surcharge, critical surface and slices, soil table and results;
- comparison Fellenius / Bishop / Spencer / Morgenstern-Price (with λ) on the critical surface;
- "Test data" pages with the slices of the critical surface.
Validation on published cases
Each published case was entered in CiviLab and compared with the reference value and with the GeoStudio SLOPE/W results (verification manual). Difference = (CiviLab − GeoStudio) / GeoStudio, same method.
| Case | Method | Published reference | GeoStudio | CiviLab 7.1 | Difference / GeoStudio |
|---|---|---|---|---|---|
| ACADS 1(a) — simple homogeneous slope | Spencer | 1.00 | – | 0.984 | – |
| ACADS 1(a) — simple homogeneous slope | Morgenstern-Price | 1.00 | 0.993 | 0.985 | −0.8 % |
| ACADS — non-homogeneous slope (3 layers) | Spencer | 1.39 | – | 1.365 | – |
| ACADS — non-homogeneous slope (3 layers) | Morgenstern-Price | 1.39 | 1.382 | 1.365 | −1.2 % |
| Arai and Tagyo (1985) — homogeneous slope | Spencer | 1.451 | – | 1.401 | – |
| Arai and Tagyo (1985) — homogeneous slope | Morgenstern-Price | 1.451 | 1.414 | 1.400 | −1.0 % |
| Greco (1996), example 4 — multilayer slope | Spencer | 1.40 to 1.42 | – | 1.421 | – |
| Greco (1996), example 4 — multilayer slope | Morgenstern-Price | 1.40 to 1.42 | 1.389 | 1.414 | +1.8 % |
| Calculation | Expected | CiviLab |
|---|---|---|
| Exact equilibrium, φ = 0: Spencer; Morgenstern-Price | 1.39264 | 1.39258; 1.39258 |
| Excel recalculation, ACADS 1(a): Morgenstern-Price (λ) | 0.98410 (0.529) | 0.98410 (0.529) |