Gabion Wall Stability Check
Check a rectangular gravity gabion wall against overturning and sliding, starting from the rock fill itself. The tool computes the gabion's own weight from its height, base width and fill density, works out the active earth thrust from the backfill, and reports the two factors of safety plus an overall pass/review status — all per metre run of wall.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the wall height H and base width B in metres — the two dimensions that set both the self-weight and the resisting lever arm.
- Optionally adjust the filled-gabion (rock) unit weight (default 16 kN/m³), the active coefficient Ka (default 0.33), the backfill soil unit weight (default 18 kN/m³) and the base friction μ (default 0.6).
- Read the gabion self-weight, the active thrust, the overturning and sliding factors of safety, and the overall status.
How it works
The gabion self-weight per metre is W = rock unit weight × B × H, treating the stack as a solid rectangle of rock. The active soil thrust is Pa = ½·Ka·γ_soil·H², acting at H/3 above the base. Taking moments about the toe gives an overturning factor of safety of W·(B/2) / (Pa·H/3), while the sliding factor of safety is μ·W / Pa. The wall is flagged OK only when overturning ≥ 2.0 and sliding ≥ 1.5.
Worked example
Worked example. For H = 3 m, B = 1.5 m, rock = 16 kN/m³, Ka = 0.33, soil = 18 kN/m³ and μ = 0.6: W = 16 × 1.5 × 3 = 72 kN/m and Pa = 0.5 × 0.33 × 18 × 3² = 26.73 kN/m. M_res = 72 × 0.75 = 54 kNm/m and M_ot = 26.73 × 1.0 = 26.73 kNm/m, so overturning FoS = 54 / 26.73 = 2.02 and sliding FoS = 0.6 × 72 / 26.73 = 1.62 — both meet the minimums, so the status is OK.
Common mistakes
- Using a solid-rock density for the fill — a packed gabion has voids, so its effective unit weight is usually 15–18 kN/m³, not the 26 kN/m³ of the parent rock.
- Applying this rectangular model to a stepped or battered gabion wall; those profiles move the centroid and need the true geometry.
- Stopping at overturning and sliding — base bearing pressure, internal course-to-course shear and global slope stability still have to be checked.
Frequently asked questions
What unit weight should I use for a filled gabion?
The effective unit weight of a rock-filled gabion is the solid-rock density reduced by the void ratio of the packing. For typical hard rock at around 26 kN/m³ with 30–40% voids, this lands near 15–18 kN/m³. The default of 16 kN/m³ is a reasonable starting value, but confirm it from the actual rock density and expected porosity.
Why does a wider base help so much?
Widening the base increases the wall in two ways at once: it adds weight (W grows in proportion to B) and it lengthens the resisting lever arm (B/2). Because the resisting moment is W·(B/2), it rises roughly with the square of the base width, so a modest increase in B can move an unstable wall comfortably past the overturning target.
Related tools
- Retaining Wall Overturning & Sliding Check
- Coulomb Earth Pressure Calculator
- Footing Reinforcement Calculator
- Active Earth Pressure (Rankine) Calculator
- Fatigue Life Estimator
- Passive Earth Pressure Calculator
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