21st CENTURY SPILLWAY: PIANO-KEY WEIR Civil Engineering Project

Civil Engg Project

Project Abstract:

Most existing free-flow spillways have a standardized shape (Ogee weir) and are
placed upon concrete gravity dam structures. Their drawback is their low specific
flow which is (in m3
/s/m) close to 2.2 h 1.5 (h being the nape depth in meters). The
control of floods is generally assured with spillways which assures the
passage of floods without incident. The cost of spillways represents a significant
part of the global cost of dams. The loss of storage as a result of sedimentation of
the reservoir can be remedied by heightening the sill of spillways which allows having
a supplementary space of storage. The search for an optimal shape of the weir which
possesses a high performance and a low cost led to the conception of a new shape of
the non-linear weir. The Piano Keys Weir (P.K.Weir), the recently developed new
shape of weir represents an effective alternative for most new dams and can
increase the storage capacity of several existing dams by spending lesser amount
than ogee weir. A P.K.Weir increases the discharge per unit width of the spillway for a
given operating head.
In the present project work, the effects of PK weir geometry on weir performance is
evaluated. Laboratory scale sectional models of PK weir and Ogee weir are
fabricated and tested for various discharges. Further the relationship between head
& discharge has been investigated.
Most of existing reservoir dams are often faced two fundamental problems, the
first relates to the control of floods which can present dam submerging risks,
the second relates to the loss of the storage capacity as a result of
sedimentation. The control of floods is generally assured with spillways
which assures the passage of floods without incident. Nevertheless, its cost
represents a significant part of global cost of dam. The loss of storage as result of
III
sedimentation of reservoir can be remedied by heightening the sill of spillways
which allows having a supplementary space of storage. The search for an optimal
shape of weir which possesses a high performance and a low cost, led to
conception of a new shape of non linear weir.
P.K.Wier recently developed new shape of weir represents an effective alternative
for most new dams and can increase the storage capacity of several existing dams
by spending lesser amount then ogee weir. A PK weir increases the discharge per
unit width of spillway for a given operating head which has been proved making a
model representing discharging phenomena in both the cases of P. K Weir as well
as Ogee Weir