Table 1: Assumptions employed in the guides on optimum diameter of diversion tunnel
| Type |
Top width, B (m) |
Average length, W(m) |
Average side slope |
Freeboard, F (m) |
|
| Embankment |
5 |
100 to 1200 |
1H:2.25V |
1.5 |
|
| Length, L (m) |
Diameter, D (m) |
Longitudinal slope, S (-) |
Lining thickness, T(cm) |
|
| 100 to 1400 |
3 to 15 |
0.005 (0.001 to 0.015) |
30 to 75, varying linearly with D |
|
| Discharge, Q (m3/s) |
Manning Roughness Coefficient, n |
|
Flow regime |
Exit |
| 50 to 1900 |
0.014 for RC lining |
0.022 for shotcrete |
0.030 for natural rock |
Pressurised (full flow) |
Unsubmerged |
| Type I (n=0.014 |
Type II (n=0.022) |
Type III (n=0.030) |
Rock bolts |
Shotcrete |
|
| Rock bolts + Shotcrete + Reinforced concrete (RC) |
Rock bolts + shotcrete |
Little rock bolts + little shotcrete |
~3m long |
10cm thick with steel wires |
|
| Tunnel excavation, C1 (US$/m3) |
Concrete lining C2 (US$/m3) |
Support (rock bolts + shotcrete), C3 (US$/m2) |
Fill for the cofferdam, C4 (US$/m3) |
|
| 8 to 48 |
40 to 140 |
24 to 70 |
2 to 8 |
|
|
