Hydraulic Structures: Fourth Edition

Ifbandb 1 are the thrift basin and lock widths, handh 1 are the basin
and lock depth increments, nis the number of thrift basins, eis the excess
head allowed during the operation (it would take too long to wait for com-
plete level equalization) and xis the residual depth to be filled from
(during filling) or discharged to (during emptying) the canal, then, assum-
ing the lock and basin to have equal lengths:

b 1 h 1 bh or Kb 1 /bh/h 1 (1),

xeheh 1  2 eh 1 h 2 e(K1)h 1. (11.24)

For a total lift, H, and the lift provided by the basins, nh 1 ,

Hxnh 1 ,

h 1 (H x)/n. (11.25)

Thus, from equations (11.24) and (11.25), the head loss

x (11.26)

or the relative head loss



H

x

hr . (11.27)

The efficiency, , of the thrift lock is

 1 hr . (11.28)

n



Kn 1

n 2 en/H



Kn 1

K 1



nK 1

K 1  2 en/H



nK 1

2 en(K1)H



nK 1

THRIFT LOCKS 487

Fig. 11.15 Thrift basins