field visit to Victoria dam
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Transcript of field visit to Victoria dam
Field Visit to Project of Victoria Dam and
Hydro Electric Power Station
On 13th July 2016
Visited Staff members and students of civil engineering department of
Sir John Kotelawala Defence University
Created by: D.S.ARACHCHIGE (ENG/13/023)
Content
1. History Victoria project
2. Project description
3. Introduction of Arc dam
4. Description about Victoria dam
5. Instrumentation and monitoring
6. Victoria power station
7. Conclusion
History of the Victoria project
Mahawali master plan is most effective plan executed to resolve major problems emerge in Sri
Lanka. Which mainly focused problems of insufficient water supply to agriculture, electricity
of the country, unemployment, less facility to inland fishery and flooding. Under Mahawali
master plan there are 12 projects, from those Victoria multipurpose complex project is the
biggest valued of 9.8 billion (1980-1984) project construction completed and opened by British
Prime Minister Margaret thatcher in 1985. Behind this national man-made heritage has an
interesting story about Sri Lankan politicians of former Hon president J.R.Jayawaradena and
Gamini Disanayaka how the funds found from British government and Sri Lankan government
encouragement. In the inauguration day Gamini Disanayaka declared free of charge to visit the
Victoria dam to all Sri Lankan as a memorize monument who work on the project.
Project Description
Victoria Dam built across the Mahawali
gaga narrow and deep valley, beside
mountains are Bogalakanda and Denigala,
located on upstream of Victoria waterfall
130 miles away from river mouth. Access to
the site 4 miles long jungle tract from
Teldeniya.
Consultant Alexander Gibb
CECB
Contractor
Balfour Beatty Nattall UK
Mechanical- Boving UK
Electrical - Balfour Klipatric UK
Technical information of the dam and reservoir are
Catchment area – 1891 𝑘𝑚2
Nuwara Eliya, Kandy and Matale are districts in the catchment
Mahawali gaga and Hunu gaga are joining to reservoir
Flood level – 441.2 m MSL
Spilling level – 438 m MSL
Surface area of reservoir - 23.7 km2
gross capacity of the reservoir – 722 Mm3
active capacity - 689 Mm3
Minimum water supply level – 370m MSL
dam type – Cupola or Double- curvature Arc Dam
crest height – 122 m and crest length – 520 m
Automated radial spillway 08 gates, one gate 8m height and width 12.5m
Spilling capacity 7900 cumsec
Two sluice gates of 4m x 3m
Annual regulated discharge of 760 cumsec for irrigation releases
Introduction of arc dam
Arc dam are more reliable and economical than other modern concrete dams. It is structurally
more efficient rather than gravity or buttress dam, reason of arc dam reduce the required
concrete volume. Cupola or double-curvature arc dam is derivative of simple arc dam, which
has complex curvature horizontal and vertical plane. Therefore reaction force vary with dam
face due to double curvature. Structural function of dam is transmitting water load to abutments
or valley. So abutment or valley stability most critical to structural integrity and safety.
Description about Victoria dam
As undergraduate civil engineers, it is important know entire work such as design and
construction of the dam. More important thing is Victoria Dam designed by British engineers
they applied innovative technology to control gates and dam construction. Especially these
automatically opening gates needs power only to close the gate. They have won the award of
“Innovative Design in Civil Engineering" commenced by the institute of civil engineer in UK.
Geological conditions are most favorable, foundation of the dam hard and slightly fractured
gneiss deposited about 8 ft. to 17 ft. in fragmental and weathered rock. Shape of the valley also
favorable to construct arc dam.
Dam was constructed by using 480 thousand cubic meter concrete volume and reinforcement
are used at the spillway gates. Maximum size of the aggregates used 150mm.There have been
used low heat Alkali cement and ice to control the temperature and avoid occur cracks. Dam
has 35 blocks like cantilever beams along crest length. Dam has 7 galleries in different
elevations to access internal remedies and inspections. Following figure shows the how the
blocks were constructed during construction.
(Source from Victoria Dam office)
These galleries are named
A,B,C,D,E,F and G else
drainage gallery also
placed beside of the
foundation. And blocks
named rigth side even
numbers and left side odd
number.
Victoria dam has semi-automatic radial gate system innovative design by Gibb. Counter
balance has more weight than gate, when water level up to spilling level hydraulic ramp release
the gate and gate will open, only power needed to close the gate. There is 08 gates which are
opened in sequential manner.
Victoria Dam instrumentation and monitoring
During the construction of the dam also have provided instruments and assess continous
monitering of the dam behavior. Among these instruments are normal and inverted pendulum,
crest leveling studs, survey targets on the downstream face, extensometer, piezometers / drain
holes and strain gauges. On our vist we observed normal and inverted pendulam. Normal
pendulum used to mesure the dam defelection and inverted pendulum used to measure
foundation deflection. there are 07 normal and inverted pendulums located at block
nu.02,05,12,17,20,25 and 26. Mainly blocks deflection are meseared where water filled in
maximum level and minimum level. In past records showed that in 1985 imponding year level
of 420m MSL maximum deflection more than 40mm, when water level reduced showed
opposite direction deflection.
Other instrument such as clinometers and level studs, face target are used to measure
defelection of dam and foundation respectively. Level studs also used to measure upward
movement of the dam. Site engineers continous monitoring conducted check the behavior of
the dam do the renovation works. Our visited time dam aboutment renovation works are going
on.
( Normal pendulum, Inverted pendulum, clinometer and drainholes )
Victoria power station
Power station located downstream of the Victoria dam through 5.8 km long and 6.2m
diameter tunnel. This headrace tunnel connected to a 116m depth and 21m diameter surge
chamber. Power tunnel capacity about 140 cumsec. From surge chamber to valve house a steel
lined tunnel 405m long was joined, from there three penstocks were installed 190m long and
3m diameter penstocks. Design head is about 190m. Basic concept of energy transformation is
water potential energy transform to kinetic energy and through mechanical electricity produce.
Currently Victoria power has station 03 Francis type of turbine in running condition which are
generating 210MW electric power to the national grid. Selection of Francis type turbine is
rather than Pelton efficiency and no need nozzles to inject water.
Semi-umbrella type generates were installed above turbine through shaft which
generate 2.5 kV voltage. Stage 2 of the Victoria complex project is still incomplete. Proposed
project has two power tunnels but one tunnel stopped 100m and sealed from concrete at the
Victoria reservoir power intake. So total turbine will be 06.
(Source: Headworks Division of Mahaweli Authority presentation)
Conclusion
Sri Lankan civil engineering history Victoria dam is one highest ranked example
of used modern technology at that situation. Local consultant part was done by CECB
but without British engineering knowledge it not reliable. In the conclusion like to state
that politicians behind this project did tremendous decision to accomplish the aims. At
that days people said this project enable us to supply electricity to other countries.
After 4 year commencing project government achieved higher revenue compare
with project value. From the project inland fishery industry also developed and flooding
of downstream villages also protected. Victoria dam become a remarkable and heritage
value land mark due to that’s attraction and engineering knowledge.
As civil engineer its design and construction and maintenance works cannot be
excluded. This is cupola arc dam, so traditional ring theory is not applicable to cupola
profile need complex analysis of FEA. Here important to know about transverse
contraction joints called interblock joints which are 15m wide along dam. Joints are
made necessary by shrinkage and thermal characteristic of mass concrete. That permit
minor differential movement between adjacent blocks. To control seepage water
barriers were installed.
More than 70 thousand works devoted their effort to construct. Dam safety is
most priority because of downstream Randenigala, Rantabe dams are located. If any
situation of Victoria dam failure occurred higher possibility to break down downstream
dams. Therefore resident engineers and technicians are doing valuable job of
monitoring works and renovation works to keep dam stability last long. Victoria dam
passed 30 year without any problems.