---
title: "Short note: slab culvert"
subject: "Transportation Engineering I"
chapter: 4
key: "semester_6/transportation_engineering_i:slab-culvert-note"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/slab-culvert-note
site: BCT Engineering
---

# Short note: slab culvert

Transportation Engineering I · Chapter 4: Highway Drainage

- Asked in: 2065 Chaitra (old course), 4 marks
- Video: [RC Slab Culvert | Slab Culvert | RC Slab Culvert as per IRC | Indian Road Congress | Culvert Slab](https://www.youtube.com/watch?v=GCbQf7QNR_k) — Civil Engineering Mastery
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/slab-culvert-note
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-4

## Question

Write a short note on slab culvert and its elements.

## Short answer

A slab culvert is an RCC deck on abutments spanning up to 6 m over a rectangular waterway, suitable for firm foundations. It comprises deck slab, abutments, wing/return walls, foundation below scour depth, bed protection (apron, cut-off walls), parapet, and weep holes.

## Answer

A **slab culvert** is a cross-drainage structure in which a reinforced concrete slab (deck) rests on two abutments, with an open rectangular waterway below. It is used for spans of up to about 6 m when the foundation is firm and the stream bed is stable, and it needs little height between the bed and the road level. In Nepal it is widely used on hill and Terai roads.

#### Elements
1. **Deck slab**: RCC slab designed for IRC wheel loads (Class A / 70R, as adopted in DoR practice). Bearing on abutments through a bearing strip (a simple bitumen/felt layer).
2. **Abutments**: stone masonry or concrete walls that support the slab and retain the road fill.
3. **Wing walls and return walls**: guide the flow, retain the embankment, and protect from scour.
4. **Foundation**: strip or raft footing on firm soil or rock, taken below the scour depth.
5. **Bed protection (floor/apron, curtain walls and cut-off walls)**: upstream and downstream to prevent undermining.
6. **Parapet / kerbs and wearing coat**: provide safety to traffic and a riding surface.
7. **Drainage**: weep holes in the abutments.

```text
 parapet |-- wearing course --| parapet
         |=== RCC deck slab ===|
  wing   | abutment   abutment | wing
  wall   |_____waterway_______| wall
          apron + cut-off walls
```

Advantages: the open waterway is easy to inspect and clean, and the structure is quick to build. A disadvantage is that it needs abutments on good foundation, so it is not suited to soft soil (where a box culvert is better).

## Check yourself

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

1. A slab culvert consists of:
   A. A masonry arch
   B. A box
   C. RCC deck on two abutments over an open waterway
   D. A buried pipe
   Answer: C. Used for spans up to about 6 m with firm foundations. (Key point: Definition)

2. Slab culverts are not suited to:
   A. Soft soil, where a box culvert is better
   B. Rock
   C. Stable bed
   D. Firm foundation
   Answer: A. They need abutments on good foundation. (Key point: Foundation)

3. Wing walls and return walls:
   A. Guide flow, retain embankment and protect from scour
   B. Hold the pipe
   C. Carry the deck
   D. Form the deck
   Answer: A. They also protect the structure. (Key point: Wing walls)

4. An advantage of slab culvert is:
   A. Suits soft soil
   B. Open waterway easy to inspect and clean
   C. No abutments
   D. Needs no foundation
   Answer: B. It is also quick to build. (Key point: Advantage)

## Related in other subjects

- [RCC slab culvert: brick, wearing coat, GI pipe, steel](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aslab-culvert-a-fig-b) — Estimating and Costing, chapter 6
- [RCC slab culvert: excavation, PCC foundation, slab](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aslab-culvert-j) — Estimating and Costing, chapter 6
- [Slab culvert: excavation and brickwork](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aslab-culvert-l-brick-earthwork) — Estimating and Costing, chapter 6
- [RCC slab culvert 1.5 m span: four items](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aslab-culvert-n-four-items) — Estimating and Costing, chapter 6