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.