For concreting tunnel linings, transportation of concrete is done by:
Correct Answer: D. Pumps
📚 Detailed Explanation: Pump Transport for Tunnel Lining Concrete
Why D (Pumps) is correct: Tunnel lining presents unique challenges: the work face is deep underground, access is limited to one opening, the lining geometry is curved (arch), and concrete must often be placed overhead. Conventional transport (pans, wheel barrows) is impossible or highly impractical. Concrete pumps are the standard solution — they push concrete through rigid or flexible pipes of 100–200 mm diameter directly to the placement point.
Pump Concrete (Pumpcrete) Specifications
| Parameter | Value |
|---|---|
| Slump requirement | 80–100 mm (medium workability) |
| Max. horizontal distance | Up to 400 m |
| Max. vertical height | Up to 80 m (horizontal) / 50 m (vertical, depending on source) |
| Pipe diameter | 100–200 mm |
| Pre-pump treatment | 1:2 cement slurry pumped first to lubricate pipes |
| Max. aggregate size | One-third of pipe diameter |
Why Other Methods Fail for Tunnels
| Method | Why Unsuitable for Tunnels |
|---|---|
| Pans (head loads) | Impractical in confined tunnel; overhead lining impossible |
| Wheel barrows | Short range only; cannot reach overhead arch sections |
| Containers / buckets | Require crane headroom; not available inside a tunnel |
| Pumps | Can reach any point via flexible pipe; handles overhead placement |
- Tunnel lining concrete is placed by pumps through 100–200 mm diameter pipes.
- Pump concrete requires slump of 80–100 mm for flowability through pipes without segregation.
- Pipe joints must be leak-proof; max aggregate size ≤ 1/3 of pipe diameter.