A gravity wall resists backfill thrust by its own mass alone, with no reinforcement at all — which means there's no flexural or shear design step, just four stability checks, and the resultant-eccentricity check keeping the base in compression everywhere is usually the tightest of the four.
Every check above runs automatically inside the Structyze Gravity Wall module — this particular module is part of the full desktop catalogue rather than the free browser trial, since the trial only carries a curated flagship set. You can still try the free trial modules right now to see the same calculation style in action on RCC Beam, Column, Slab and a handful of others.
The Example We'll Use
- Wall height 2.5 m, top width 1.5 m, base width 2.2 m (battered front face)
- Backfill γ = 18 kN/m³, φ = 30° (Ka = 0.333), no surcharge
- Concrete unit weight 24 kN/m³ (mass concrete)
- Allowable bearing 150 kN/m², friction coefficient 0.5
Working Through It
Active thrust Pa = 0.5(0.333)(18)(2.5)² ≈ 18.7 kN/m, acting at H/3 above the base, giving an overturning moment of 15.6 kN·m/m.
Self-weight comes from summing the wall's rectangular and battered (triangular) components separately, each at its own centroid: total W ≈ 111 kN/m, giving a resisting moment of 103.9 kN·m/m. Overturning FoS = 103.9/15.6 ≈ 6.66 — a huge margin, and sliding FoS = 0.5(111)/18.7 ≈ 2.97, also comfortable.
The resultant eccentricity, though, is a different story: e = |0.795 − 1.1| = 0.305 m against a middle-third limit of B/6 = 0.367 m — utilisation 0.83, by far the tightest of the four checks, since it's the one where the plain-concrete section has zero tension capacity to fall back on.
What Governs, and Why
Resultant eccentricity governs at utilisation 0.83 — far tighter than overturning (0.23) or sliding (0.51) despite both of those having their own formal safety factors. Since the wall is unreinforced, anything past the middle third would demand tensile stress the plain concrete simply cannot supply; widening the base or increasing the batter are the only fixes if this check fails.
Where Structyze Takes Over
Every check above runs automatically inside the Structyze Gravity Wall module — this particular module is part of the full desktop catalogue rather than the free browser trial, since the trial only carries a curated flagship set. You can still try the free trial modules right now to see the same calculation style in action on RCC Beam, Column, Slab and a handful of others.
For Gravity Wall and the rest of the full catalogue — 80+ components across RCC, Steel, Composite, Timber, Masonry and more, across 20+ design codes — buy the full Structyze desktop app or see everything it does on the Software page.
Quick FAQ
Why is eccentricity the binding check for an unreinforced wall?
A reinforced section can carry some tension in its steel even if the concrete alone would crack; a genuinely unreinforced (mass) section cannot — keeping the resultant within the middle third of the base keeps the entire section in compression, which is the only way a plain-concrete wall stays structurally valid.
Does IS 456 give specific gravity-wall provisions?
No — IS 456 is written for reinforced concrete and gives no specific mass-concrete retaining wall rules, so gravity wall design follows standard mass-concrete and geotechnical practice: overturning, sliding, eccentricity and bearing, with no flexural or shear design since there's no reinforcement to design.
Final Thoughts
A gravity wall's eccentricity check running far tighter than its overturning or sliding factors of safety is a pattern that's easy to miss if you only check the 'named' stability ratios by hand and stop there.