Global, tieback and compound stability¶

Global stability (Bishop)¶

Check with simplified Bishop on a circular surface, A2+M2+R2 approach: reduced parameters (γ_tanφ′ = γ_c′ = 1.25) and threshold FS ≥ γ_R2 (1.1 static · 1.2 seismic). The circle is automatic (it passes below the structure) or can be constrained with the three downhill/uphill/base points; the reinforcements crossing the surface contribute with the lesser of R_d and the pullout of the portion anchored beyond the circle.

Result of global stability and of the internal tieback and compound checks

Internal checks: tieback and compound¶

When the facing is battered the structure behaves as reinforced soil: besides global stability, the program analyses a fan of circles exiting on the facing at the reinforcement levels:

Tieback — surface entirely inside the reinforced volume (entry on the crest);
Compound — exit on the facing but entry beyond the block (it also cuts the retained soil).

For each family the program reports the minimum FS with the γ_R2 comparison, the reinforcements crossed and the critical circle, drawn dashed (purple for tieback, blue for compound). The Animate internal checks button replays the fan of circles that were tried; press it again to go back to the static drawing.

Global critical circle in red, tieback in purple and compound in blue

Tip

With a 90° facing the structure behaves as a wall and the external checks usually govern; as α decreases (85° and below) the internal checks become significant.

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