---
title: "Guidelines and design considerations, retaining walls"
subject: "Foundation Engineering"
chapter: 3
key: "semester_5/foundation_engineering:retaining-wall-guidelines"
source: https://www.bctengineer.com/q/semester_5/foundation_engineering/retaining-wall-guidelines
site: BCT Engineering
---

# Guidelines and design considerations, retaining walls

Foundation Engineering · Chapter 3: Lateral Earth Pressure Theories and Retaining Walls

- Asked in: 2078 Kartik, 5+3 marks
- Video: [Design considerations of Retaining wall /MOD 3- LEC 05 /MTECH-KTU /03CE7083:SDF](https://www.youtube.com/watch?v=8EDGchWEfZE) — CIVIL Enlightener
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/foundation_engineering/retaining-wall-guidelines
- Whole chapter: https://www.bctengineer.com/md/semester_5/foundation_engineering/chapter-3

## Question

What general guidelines are adopted before checking the stability of different types of retaining walls? Explain the different design considerations for retaining walls.

## Short answer

Select wall type by height, assume trial dimensions (base 0.5–0.7H, stem H/12–H/10), determine soil loads and active pressure (Rankine or Coulomb), then check overturning (FS≥2), sliding (FS≥1.5), bearing (FS≥3) and resultant within middle third. Use free-draining backfill, weep holes, filter, account for seismic/surcharge effects, and design stem/heel as cantilever.

## Answer

#### General guidelines before checking stability
1. **Choose the wall type from height:** gravity wall for about 3-4 m, cantilever for 4-8 m, counterfort/buttressed for more than 8 m or with large surcharge.
2. **Assume trial dimensions** from the usual proportions (base width 0.5-0.7 H, stem and slab thickness H/12-H/10, toe about B/3).
3. **Find the soil data:** unit weight, $\phi$, $c$ of backfill and foundation soil, water table, bearing capacity.
4. **List the loads:** self-weight, soil weight over heel, active thrust, surcharge, water pressure, seismic force.
5. **Select the earth pressure theory** (Rankine for vertical back with smooth wall assumption; Coulomb for rough and inclined walls) and compute the active pressure; ignore passive pressure in the top 0.5-1 m, or take only a reduced part.
6. **Check** overturning, sliding, bearing, tension at base and overall stability.

#### Design considerations
- **Backfill:** preferably free-draining granular material (sand, gravel); avoid clay, which gives high and variable pressure.
- **Drainage:** weep holes (100 mm at 2-3 m spacing), a filter or geotextile and a longitudinal drain at the heel to remove water pressure.
- **Stability requirements:** FS against overturning $\ge 2$, sliding $\ge 1.5$, bearing $\ge 3$; resultant within the middle third.
- **Foundation depth:** below frost, scour and softened soil; use a shear key if sliding is a problem.
- **Structural design:** stem as a cantilever, heel and toe slabs in bending and shear; reinforcement on tension faces.
- **Joints:** expansion joints about 20-30 m and contraction joints about 10 m in concrete walls.
- **Seismic effect and surcharge** where relevant; allow for the effect of tension cracks in cohesive backfill.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which wall type is suggested for heights more than 8 m or with large surcharge?
   A. Gravity
   B. Cantilever
   C. Counterfort/buttressed
   D. Sheet pile
   Answer: C. Gravity about 3-4 m, cantilever 4-8 m, counterfort for more than 8 m. (Key point: Wall type by height)

2. Preferred backfill and drainage arrangement is:
   A. Clay with no drains
   B. Free-draining granular fill with weep holes, filter and heel drain
   C. Silt with small holes
   D. Saturated sand
   Answer: B. Granular fill with weep holes reduces water pressure; clay gives high and variable pressure. (Key point: Backfill and drainage)

3. Required factors of safety against overturning, sliding and bearing are:
   A. 1.5, 2, 2
   B. 2, 1.5, 3
   C. 3, 2, 1.5
   D. 1, 1, 1
   Answer: B. Overturning >= 2, sliding >= 1.5, bearing >= 3, with the resultant in the middle third. (Key point: Stability factors)

4. Typical spacing of contraction joints in concrete walls is about:
   A. 10 m
   B. 1 m
   C. 50 m
   D. 100 m
   Answer: A. Contraction joints about 10 m, expansion joints about 20-30 m. (Key point: Joints)

## Related in Foundation Engineering

- [Stability checks of retaining walls](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Astability-checks-retaining-wall) — Foundation Engineering, chapter 3, asked 2×
- [Proportioning of retaining walls](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aproportioning-retaining-walls) — Foundation Engineering, chapter 3, asked 3×
- [Braced cut design versus retaining wall](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Abracing-vs-retaining-wall) — Foundation Engineering, chapter 4, asked 2×
- [Flexible versus rigid retaining structures](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aflexible-vs-rigid-retaining) — Foundation Engineering, chapter 5, asked 3×
- [Why design for active pressure only](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Apassive-pressure-neglect) — Foundation Engineering, chapter 3, asked 4×

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