--- title: "Types of retaining walls" subject: "Transportation Engineering I" chapter: 5 key: "semester_6/transportation_engineering_i:retaining-walls-types" source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/retaining-walls-types site: BCT Engineering --- # Types of retaining walls Transportation Engineering I · Chapter 5: Hill Roads - Asked in: 2071 Bhadra, 8 marks; 2068 Bhadra (old course), 8 marks; 2067 Mangsir (old course), 4 marks; 2065 Chaitra (old course), 4 marks; 2062 Jestha (old course), 8 marks (asked 5 times) - Video: [Retaining Walls Explained | Types, Forces, Failure and Reinforcement](https://www.youtube.com/watch?v=UummY_mo85Y) — Structures Explained - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/retaining-walls-types - Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-5 ## Question Describe the different types of retaining walls (retaining structures) used in road construction. List out the basis of their selection. ## Short answer Common types includeravity walls (dry stone, masonry, concrete), cantilever RCC, counterort, gabon, crib, reinforced earth and breast walls. Selection depends on height, backfill and foundation conditions, local material availability, cost, drainange, seismic demand, space and maintenance. ## Answer A **retaining wall** is a structure built to hold back earth (or water) on one side where the ground level changes abruptly, to carry the road on the hill side or to protect the valley-side fill. Types used in road construction are: #### 1. Gravity walls Resist the earth pressure by their own weight. - **Dry stone masonry**: stone placed without mortar. Cheap, flexible and drains freely, for low heights (up to about 3 m). - **Stone masonry in cement/lime mortar**: for heights up to about 6 m, with weep holes. - **Plain concrete**: where stone is not available. #### 2. Semi-gravity walls Plain concrete with a little reinforcement, thinner than a gravity wall. #### 3. Cantilever RCC walls An inverted T or L shaped RCC wall; the stem acts as a cantilever, and the weight of the soil on the heel provides stability. Economic up to about 6 to 8 m. #### 4. Counterfort and buttress walls RCC walls with vertical ribs (counterforts, behind the stem; buttresses, in front) at regular spacing, which support the stem. For heights above about 8 m. #### 5. Gabion walls Rectangular wire-mesh boxes filled with stones, stacked in steps. They are flexible, permeable, easy to build with local labour and tolerate settlement; very popular in Nepal on hill roads. #### 6. Crib walls Interlocking precast concrete or timber members filled with soil or gravel; are flexible. #### 7. Reinforced earth (MSE) walls Layers of compacted fill with strips, grids or geotextiles tied to facing panels. They are economical for high walls and perform well in earthquakes. #### 8. Anchored / soil-nailed walls and sheet piles For steep unstable cut slopes; use ground anchors or nails. #### 9. Breast walls Built on the hill side to support a cut face, and prevent rock fall (as opposed to retaining walls on the valley side). ```text Gravity wall Cantilever RCC Gabion /| | stem ___ / | | |___|__ / | soil ___|__ heel |_____|__ /___| |toe | steps ``` #### Basis of selection - Height of the wall and the type and strength of the backfill. - Bearing capacity and depth of the foundation soil, and settlement. - Availability of local materials (stone, sand, cement) and skilled labour. - Cost and construction time. - Drainage conditions (provide weep holes, filter) and ground water. - Seismic conditions and flexibility. - Space available and aesthetics. - Ease of maintenance and repair. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How does a gravity retaining wall resist earth pressure? A. By its own weight B. By tension in the stem only C. By ground anchors D. By soil weight on the heel Answer: A. Gravity walls (dry stone, masonry, plain concrete) rely on their own weight. (Key point: Gravity walls) 2. In a cantilever RCC retaining wall, what provides stability? A. Its large plain concrete mass B. The stem acting as a cantilever, with the weight of soil on the heel C. Weep holes D. Counterfort ribs in front Answer: B. The inverted T or L section uses the stem as a cantilever and the backfill weight on the heel, economic to about 6 to 8 m. (Key point: Cantilever wall) 3. Why are gabion walls popular on hill roads in Nepal? A. They are rigid and impermeable B. They need heavy cranes C. They are flexible, permeable, easy to build with local labour and tolerate settlement D. They only work above 8 m Answer: C. Stone-filled wire boxes are flexible and permeable and use local labour and materials. (Key point: Gabion walls) 4. Which is a basis for selecting the type of retaining wall? A. Colour of the wall B. Name of the contractor C. Distance to the nearest town only D. Wall height, backfill, foundation bearing capacity, local materials, cost, drainage and seismic conditions Answer: D. Height, soil, foundation, materials, cost, drainage and seismic flexibility govern the choice. (Key point: Selection basis) ## Related in Transportation Engineering I - [Retaining and slope protection structures](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aretaining-slope-protection) — Transportation Engineering I, chapter 5 - [Hill road drainage structures](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ahill-drainage-structures) — Transportation Engineering I, chapter 5, asked 4× - [Macadam road construction method](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Amacadam-construction) — Transportation Engineering I, chapter 1 - [Desirable properties of road aggregates](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aaggregate-desirable-properties) — Transportation Engineering I, chapter 6, asked 5× - [Roadside structures and landslide stabilisation](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aroadside-structures-landslide) — Transportation Engineering I, chapter 5 - [Factors controlling hill road alignment](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ahill-alignment-factors) — Transportation Engineering I, chapter 5, asked 2× ## Related in other subjects - [Proportioning of retaining walls](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aproportioning-retaining-walls) — Foundation Engineering, chapter 3, asked 3× - [Guidelines and design considerations, retaining walls](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aretaining-wall-guidelines) — Foundation Engineering, chapter 3 - [In-plane and out-of-plane behaviour of masonry walls](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Ain-plane-out-of-plane-behavior) — Design of Timber and Masonry Structures, chapter 6 - [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×