126 CIVIL WORKS GUIDELINES FOR MICRO-HYDROPOWER IN NEPAL
Figure 8.5 Proposed machine foundation section for Example 8.1
Notes
1. All dimensions are in mm.
2. A minimum of six 20mm diameter, 700mm long anchor bars are to be used to fix the base frame
to the machine foundation.
3. 10 mm diameter Tor steel bars are to be used for reinforcement. Maximum spacing to be 150mm
in turbine pit and 200mm on other faces. Lap length shall be 400 mm minimum.
4. Minimum reinforcement cover shall be 50mm.
5. Structural concrete shall be 1:1.5:3 mix.
8.5 Tailrace
8.5.1 GENERAL
The tailrace is the final civil structure that conveys the design
flow. Similar to the headrace, open channel or pipes can be
used for the tailrace section. Tailrace channels of the Jhankre
mini-hydro and Salleri Chialsa schemes are shown in
Photographs 8.5 and 8.6 respectively.
Often, inadequate attention is given to the design and
construction of the tailrace since the flow at this stage does
not contribute towards power production. However, such a
practice can result in inadequate depth of the tailrace pit or
erosion of slopes, which could threaten the powerhouse
structure.
8.5.2 DESIGN OF THE TAILRACE CHANNEL
Design of the tailrace channel is similar to that of the headrace
canal discussed in Chapter 4. However, since headloss does
not need to be minimised a higher velocity can usually be
Photo 8.5 Tailrace channel of the Salleri Chialsa mini-hydro scheme