---
title: "Short note: breast wall"
subject: "Transportation Engineering I"
chapter: 5
key: "semester_6/transportation_engineering_i:breast-wall-note"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/breast-wall-note
site: BCT Engineering
---

# Short note: breast wall

Transportation Engineering I · Chapter 5: Hill Roads

- Asked in: 2065 Chaitra (old course), 4 marks; 2062 Jestha (old course), 4 marks (asked 2 times)
- Video: [Effect of earth pressure on the Breast wall](https://www.youtube.com/watch?v=uj2rLhDYsNE) — Highway Guru
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/breast-wall-note
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-5

## Question

Write a short note on breast wall.

## Short answer

A breast wall supports a hillside cut against small slips and erosion. Built of stone masonry or gabion, 3–5 m high, with weep holes and a drainage layer, it stabilizes the cut face, reduces excavation width, and is used with a catch drain above.

## Answer

A **breast wall** is a wall built on the hill side of a hill road, against a cut slope, to support the slope face and prevent small slips, rock fall, and weathering or erosion of the cut face. It is not intended to resist the full thrust of a retained mass of fill, but to stabilise the cut face and the slope material above it (IRC:SP:48).

#### Features
- Constructed in **stone masonry** (dry or in cement/lime mortar), plain/reinforced concrete or gabion; the wall rests on firm rock or soil.
- Height typically 3-5 m; if the cut is higher, the wall is built in tiers with berms.
- **Weep holes** (75-100 mm, at about 2-3 m spacing) and a **filter/drainage layer** behind it release the pore water pressure.
- The back face is kept very close to the cut slope (front face batter about 1 in 4 to 1 in 3); the space behind is filled with the excavated material or packed with stones.
- The top of the wall is connected to the drainage system, and the **side drain** runs along its base; the top of the cut above is protected by a **catch drain** and vegetation.

```text
   hill slope  \
                \ cut face
                 |#| breast wall
                 |#|  weep holes
   ==============|#|===  road
```

#### Functions
- Supports the hillside cut, preventing slides.
- Protects against erosion and weathering.
- Reduces the width needed for cut slopes, saving land and excavation.

On the valley side, a retaining wall is used instead.

## Check yourself

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

1. What is a breast wall for?
   A. Holding a full thrust of valley-side fill
   B. Supporting the hill-side cut face and preventing small slips, rockfall and weathering
   C. Carrying a bridge
   D. Retaining a river
   Answer: B. A breast wall is built against a cut slope on the hill side, not to retain a deep fill. (Key point: Purpose)

2. Why are weep holes and a filter layer provided?
   A. For appearance
   B. To store water behind the wall
   C. To increase water pressure
   D. To release pore water pressure behind the wall
   Answer: D. Weep holes (75-100 mm at 2-3 m) with a filter let water escape and avoid build-up of pressure. (Key point: Weep holes)

3. Where is a retaining wall used instead of a breast wall?
   A. Where the road is on the valley side, retaining the fill
   B. On the hill side cut
   C. Never
   D. Only above the catch drain
   Answer: A. Breast walls are on the hill side; the valley side uses a retaining wall. (Key point: Breast vs retaining)