The Hydroplus Fusegate System - four years on. S CHEVALIER - Project Engineer - Hydroplus International S T CULSHAW - Area Manager - Hydroplus International J P.FAUQUEZ - Président - Hydroplus International
SYNOPSIS. The Hydroplus fusegates can be utilized for increasing live storage capacity of dams with ungated spillways and/or for improving spiliway safety without sacrificing storage capacity they are designed to rotate (tilt) in succession when thé réservoir levé! reaches predetermined élévations thereby preventing. thé flood from overtopping thé dam. This paper discusses varying approaches in thé use of thé System to solve thé problem of safety worldwide includinu thé Dove Stone réservoir in thé North West of Enuland. INTRODUCTION. Under normal conditions fusegates increase thé, active storage area of réservoirs The labyrinth weir configuration allows for increased discharge at lower heads than conventional spillways The fusegate design allows for thé fusegates to overturn during high or extrême flood events thereby allowing more flow through thé spiliway Thèse Systems can increase thé active storage of a réservoir and increase thé discharge capacity for extrême events so that thé design flood may without overtopping thé existing dam and thus reducing or eiiminating thé need for increasing thé dam height THE CONCEPT. The Hydroplus system consists of one or more adjacent but independent fusegate units resting on thé overspill sill and held in place solely by gravity forces. The fusegates are overtopped by moderate floods In case of larger floods. some éléments are ovèrturned by rotating about lugs located at thé downstream edge of thé sill The number of units activated away is graded to suit thé hydrogrnph of thé particular expected flood and match thé required discharge flow Each unit sits freeiy on a concrète slab cemented into thé crest and consists of three parts * The faucket itop part) made of steei or reinforced concrète with can be given a labyrinth shnpe to increase thé overspill length so that moderate floods can be discharged with a relatively small head on thé lip. * The bottom chamber base made of steel or reinforced concrète. * The weil a funnelled conduit into thé chamber which begins to fill for a given réservoir level Wells are set at différent élévations. The réservoir as an asset. Thomas Telford. London, 1996
CHEVALIER ETAL 133
When réservoir level reaches a given élévation, water flows through thé well into thé chamber Pressure builts up in thé bottom chamber and when sufïîcient vertical uplift lias been mobiiized, thé fusegate rotâtes about thé abutment blocks located at thé downstream edge of thé sill. The triggering system is very précise and leaves an ample safety margin until thé réservoir level reaches thé predetermined élévation activating a given élément.
The fusegate on thé spiilway crest is acting in three différent ways depending on headwater level * As part of thé dam. as long as thé réservoir level does not exceed thé fusegate bucket top edge
* as a weir, when hendwater level is higher than thé fusegate top edge but lower than thé predetermined level causing thé fusegate to overturn * As a "fuse" or a regular spiilway gâte when headwater reaches this predetermined level and triggers thé uplift Once thé flood lias receded. thé overturned fusegate is simply lifted back on thé sill or replaced with an identicai new unit if seriously damaged E.xtensive theoretical research has been conducted on fusegate performance when spilling and rotating and thorough model testing programs were performed to validate thé matliematical approach
Testing of fusegates was performed at thé Tennessee Vailey Authority facilities at Norris (Tenn ). Thèse tests validated very precisely thé behaviour of thé Hydroplus fusegates under various circumstances and conditions. Also. Ice has been thé subject of spécifie research at thé Institute for Marine Dynamics of thé National Research Council, in St John's, Canada and at thé Scientific Research Institute of Energy Structures, in Moscow, Russia
Water inlet
Ballast
Drain hole
Underface
Abutment block
Water is spilling overthe crest
34 / THE RESERVOIR AS AN ASSET
Water inlel
Ballast Drain hole
Abutment block
Underface
The inlet stack its water Water inlet —\
Ballast
Underface
•Abutment block
The fusegate tips off
FUSEO'ATE CONFIGURATIONS. The fusegate System may form a labyrinth or straight crest to thé weir. 1 - Labyrinth Crest Fuseuates A bucket shape is used to form a labyrinth crest capable of overspilling a nappe équivalent to 30 - 150% of thé fusegate height. The bucket is open at thé upstream side An alignment of buckets forms a labyrinth crest which allows moderate floods to spill with a reduced head on thé crest. The developed length of thé labyrinth is approximateiv three times that of a concrète sill length. The bucket height is commonly 1m to 6.5m, depending on thé clients needs. 2 - Straight Crested Fuseuates There are three types of straight-crested fusegates : Emergency Fiisegntes are designed to overttirn before or just after being overtopped. They are used as back-up to conventional gâtes in thé event of very large floods or gâte maifunction. They may be 1m to 10m in height.
CHEVALIER ETAL /35
Intense Cold Environment Fiisegates are designed to be very stable and their upstream face are shaped and finished to reduce ice loading, friction and abrasion. High ff ends Fusegates are designed to withstand high heads on thé fusegate crest They are constructed to obtain thé best discharge coefficient and may be large (20m wide) and capable of remaining stable when spilling under a head of up four times their height
Oversptlllxg crest
D/S abutment btock
/ SUe abtamta bleck
Dotonstream
Concrète stU V/S seai stnp
Upstream view of îabyrinth crest ftisegate
Drain boles
Pressure cbamber
Base
Bottom view of labyrinîh crest fusegate
36 / THE RESERVOIR AS AN ASSET
CASE STUDÎES. Case I Lussas Dam in thé South-Central provides irrigation water for agriculture on thé Lussas piain The dam is an earth construction 19.5m high The spilhvay is situated on thé left bank and is 36m in length.
The runo/F pattern is governed by sudden. heavy storms on thé relativelv large catchment (26.2 km) vvhich s for a large design flood. The spiTlway vvas modified and thé fusegates installed in two summer months of 1991 to increase thé réservoir storage capacity. The réservoir was successfully filled in time for crop irrigation soon after. During a flood in thé winter of Î994 one fusegate overturned at thé correct water élévation and was replaced soon after for thé réservoir to fill for thé next crop season. * - New storaue capacity *-SilI length" " * - New spilhvay capacity * - Fusegate number *- Fusegate height * - Fusegate width , * - Slorage increase * - Spilhvay capacity increase
420,000 cubic mètres 35m 250 cubic mètres per second 10 2.15 mètres 3 5 mètres 30% 15%
Case 2 The Wanakbori pick-up Weir in Gujarat State in India was built to collect water to irrigate two hundred thousand hectares of agricultural land Subséquent constructions of several dams upstream resulted in higher flood control and so reduced by 2 mètres thé \vater head available at thé weir No conventional method was cost effective to restore thé requested head on thé 678 m long spilhvay.
The Hydroplus solution consisted in thé installation of thirty three straight crested high overspill concrète fusegates two meter high and twenty mètre long.
The first fusegate tilt for a flood of about 20 000 cubic mètres per second \vhich correspond to a 6 mètres overspill over thé fusegates. * - New storage capacity * - Sill length ~ * - New spilhvay capacity * - Fusegate number * - Fusegate height * - Fusegate width *-Storage increase * - Spilhvay capacity increase
8-4.000,000 cubic mètres 675 mètres 4~.000 mètres per second 33 2 mètres 20 mètres 100% nil
Case 3 Caillaouas Dam is at an altitude of 2.170 mètres in thé French Pyrénées, ft is a masonry structure at thé end of small but very deep natural Iake. Three straight crested fusegates hâve been installed. to improve dam safety. A flap gâte lias also been installed to discharge moderate floods. The fusegates give The extra capacity to discharge thé design flood. The combination of a flap gâte and fusegates présents thé two-fold advantage of good control of thé
CHEVALIER ETAL 1 37
réservoir level Because of thé area in \vhich thé dam is located, thé fusegates were transported and installed by helicopter The opération nianuai for thé client includes requirements for ice conditions * - Storage capacity * - Sill length * - New spilhvay capacity * - Fusegate nurnber * - Fusegate height * - Fusegate width * - Storage increase * - Spilhvay capacity increase
25,400.000 cubic mètres 7 4 mètres 29 3 cubic mètres per second 3 1 5 mètres 1 6 mètres nil 1 90%
Case 4 The Shongweni Dam is located in Kwa Zulu in Natal in thé Republic of South Africa. The dam was originally built in thé 1920's, thé ungated spilhvay was 1 26 mètres The original design flood was rated at 1 ,250 cubic mètres per second Alter inspection in 1988 thé design flood was reevaluated at 5.000 cubic mètres per second The new safety requirements were not satisficd for two reasons. (a) thé dam structure was inadéquate and (b) thé spilhvay could not discharge thé re-evaluated design flood. The client examinée! four alternatives but settled on lowering thé spilhvay by 8 mètres The spilhvay was eut back 7 9 mètres and ten 6 5 mètres high fusegates were installed The resuit was that thé réservoir level was lowered only by 1 4 mètres The first fusegate is designed to tip for a flood that occurs every 240 years Each fusegate weight was some 120 tonnes and since thé cableway sa te working load was 5 tonnes thé structural design had to be adapted to meet thé weight limitation
* - Storage capacity * - Sill length * - New, spilhvay capacity * - Fusegates number * - Fusegate height * - Fusegate width * - Storage increase * - Spilhvay capacity increase
6,600.000 cubic mètres 126 mètres 5.000 cubic mètres per sec 10 6 5 mètres 9 73 mètres nil 235%
Case 5 The McClure Dam located in New Mexico. USA is an earth structure with a maximum head of 38 6 mètres and a crest length of 234 mètres The dam was built m thé l^jO's and raised three time in 1936. 1947 and I98S In 1988 thé 17 mètres spilhvay was reconstmcted With two other gravity dams, McClure supplied domestic water to thé city of Santa Fe untiï a large crack was found in thé foundation of Two Mile dam In February 1995. thé operator was allowed by thé State authorities to transfer thé water rights to McClure dam In April 1995, eight steel fusegates were installed on thé Ogee crested sill The Hydroplus concept had successfully increased live réservoir storage capacity by 0 62 lim' and spilhvay discharge capacity by 8 per cent * - Storage capacity * - Sill lenuth
3.820.000 cubic mètres 17 3 mètres
38 / THE RESERVOIR AS AN ASSET
* - New spiliway capacity * - Fusegate number * - Fusegate height * - Fusegate width * - Storage increase * - Spiliway capacity increase
507 cubic mètres per sec 8 2.15 mètres 2.13 mètres 500 acre-feet 8%
Case 6. The Dove Stone Dam is an earth structure situated under Saddleworth Moor 8 km east of Oldham in Lancashire. Calculations and 1:21 mode! tests indicated that thé existing bellmouth in thé réservoir could approximately 160 cumecs The required discharge for thé PMF being approximately 300 cumecs an auxiliary spiliway was required to meet safety criteria Three fusegates were installed into thé new 9.8 mètre wide auxiliary spiliway The fusegates are designed to tilt off thé spillvvay 0.53, 0.58 and 0 63 mètres above thé lip of each fusegate respectively. The fusegates are designed to rotate in succession between thé 1 in 10,000 years flood event and thé PMF thereby preventing thé flood from overtopping thé dam. * - Storage capacity * - Sill length * - New spiliway capacity * - Fusegate number * - Fusegate Height * - Fusegate width * - Storage increase * - Spiliway capacity increase
5,050,000 cubic mètres 9 8 mètres 282 cubic mètres per sec 3 2.15 mètres 3 23 mètres Nil 42%
CONCLUSION. Hydroplus Fusegate Systems are being used Worldwide including thé United Kingdom, China. South America. United States of America, parts of Africa and South East Asia and areas of Europe The System has proved and established ils versatility in application, in thé use of materials. methods of construction and logistics The Hydroplus Fusegate System js a method by which dam safety and/or storage capacity can be achieved in a cost effective manner. REFERENCES.
Lempérière F., Bessière C (1992) Hydroplus submersible fusegates for surface spilhvays. Modification of dams to accomodate major floods Tueifth Annual USCOLD Lecture Séries, Fort Worth, Texas. Lempérière. F.(1992) Construction..
Overspill
fusegates.
Water
Power
&
Dam
Bessière C. (1992) Hydroplus submersible flisegates for surface spiliway. International Symposium on Dams and Extrême Floods, Granada Spain, Tomo I, Topic A : Design
CHEVAUERET4L/39
LempérièreF (1992) New solution to improve Spillways of existing or Future Arch Dams International Symposium on arch dams, Hohai University, Nanjing, China Proceedings of thé Symposium Philippe M, Winton J (1992) Overspill fusegates ANCOLD, 1992 Conférence on dams, New South Wales, Australia, Récent developments in dams Engineering Conférence papers Brenac J L. (1993) Hydropius fusegates ESHA Info N° 9, European Small Hydro Association Fauquez. JP(1993) Hydroplus, thé fusegates principle. International Conférence, Hydropower, Energy and thé Environnement, Stockholm Proceedings LempérièreF (1994) Enlarging thé capacity of existing dams. Structural Engineering International, SEI Volume 4, Number 2 Falvey H T, Snell E F A , Rayssiguier J (1994) Increasing Shongweni dam discharge capacity with a Hydroplus fusegate System. Dam Safety Modification and Rehabilitation Fourteenth Annual USCOLD Lecture Séries, Phoenix, Arizona Snell E . F A . Walford B and Gibbons (1994) F J G Shongweni to hâve record fusegates International Water Power & Dam Construction Trissler M and Crawford C (1994) Installation of a fusegate System at Shongweni dam Hydropower and Dams Hakin VV D , Trissler M (1994) Use of fusegate System to improve safety at Shongweni dam International Commission on Large Dams Eighteenth Congress on Large Dams, Durban Falvey H T, Treille Philippe (1995) Hydraulics nnd Design of Fusegates Journal of Hydraulic Engineering Vol 121, N° 7, © ASCE. USA. Sikora J, Ferns L. Bailey F , Gavillet M (1995) McClure dam spillway modifications with fusegates Proceedings of 1995 Annual Conférence of thé Association of State Dam Safety OITicials, Atlanta. Georgia, USA LempérièreF (1995) Cost effective improvements in fill dam safety Hydropower & Dams Gulati T (1995) Augmenting canal capacity through application of Hydroplus Fusegates at Mahi project of Gujarat International R&D Conférence, Water & Energy 2001, Needs Development Utilisation, NewDelhi, India, Proceedinas Water Ressources. Volume II
40 / THE RESERVOIR AS AN ASSET
RayssiguierJ (1995) Hvdropius Fusegate A substantial contribution to increasing dam storage capacity Symposium "Water in East Africa, french technologies, Nairobi Kenya, Proceedings of thé Symposium Ait AJIa A (1995) Fùsegates contribute to dam safety International Water Poxver & Dam Construction Yong.Liu (1995) Application of Hvdropius fùsegates in flood-diversion areas ofHuaihe river basin Hydropower & Dams Gulati T (1995) Atigmenting canal capacity through application Hydroplus Fùsegates at Mahi project of Gujarat. Hydropower & Dams
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