Embankment dam spillways and energy dissipators

by Prof. Hubert CHANSONThe University of Queensland, School of Civil Engineering, Brisbane QLD 4072,

Australia, E-mail: h.chanson@uq.edu.au

Clermont MEL weir in 1993

Glashutte dam, 22 Aug. 2002

Spillway Designs for Embankment Overtopping System and Earth Dams

CHANSON, H. (2014). "Embankment Dam Spillways and Energy Dissipators." in "Labyrinth and Piano Key Weirs II - PKW 2013." Proceedings of 2nd International Workshop on Labyrinth and Piano Key Weirs -PKW 2013, 20-22 Nov., Paris-Chatou, France, CRC Press, pp. 23-37 (ISBN 978-1-138-00085-8).

Introduction

Embankment failure & breach development

Minimum Energy Loss weirs

Embankment overflow stepped spillways

Precast concrete blocks

Gabions & Reno mattresses

Design considerations

Introduction

Embankment = earthfill structures

ApplicationsDamsRiver training / Flood protectionCoastal protections

Tsunami barrierStorm surge barrier

Natural lakes & Landslide damsMan-made flooding (during wars)

Kyoto, Japan

Sorpe dam, Germany

New Orleans, USA in 2005 (Hurricane Katrina)

EmbankmentsEarthfill structures � Erodible systems when overtoppedLevees, Dykes

Dale Dyke dam (UK)Construction: 1863Failure: 11 March 1864(piping, poor construction)150 lives lost

South Fork dam (USA)Construction: 1838-1853Failure: 31 May 1889(spillway capacity

& construction)2,209 lives lost

Lake Ha! Ha! (Canada)Failure: July 1996(spillway capacity)

Opuha Dam Failure on 5 February 1997

Opuha dam (NZ)Construction: 1996-1999Failure: 5 February 1997(outlet capacity)

Glashutte dam (Germany)Construction: 1953Failure: 12 August 2002(spillway capacity)

Downstream flooding and damageImages courtesy of Dr Bornschein

Embankment failure & breach development

Relatively slow failure processTeton dam (USA, 100 m high) 12 h to drain reservoir (1976)

Zeyzoun dam (Syria) breach opening = 3 ½ h (2002)

Glashutte dam (Germany) 4 hours overtopping +breach opening = 30 min (2002)

Zeyzoun Dam Failure on 4 June 2002

Embankment failure = dam break but ….

Embankment breach development & inlet shape

Sequence of 8 shots within 20 s – Non-cohesive embankment overtopping model

Natural scour = similarity with MEL inlet(McKAY 1970, CHANSON 2003 JHE)

Merriespruit tailings dam failure in 1994 (Courtesy of Pr A. FOURIE)

Saaiplaas tailings failure in 1993

Island of Capri canal

CHANSON, H. (2004). "Overtopping Breaching of Noncohesive Homogeneous Embankments. Discussion." Journal of Hydraulic Engineering, ASCE, Vol. 130, No. 4, pp. 371-374.CHANSON, H. (2005). "The 1786 Earthquake-Triggered Landslide Dam and Subsequent Dam-Break Flood on the DaduRiver, Southwestern China. Comment." Geomorphology, Vol. 71, pp.437-440.

Analogy with Minimum Energy Loss (MEL) culvert inlet

MEL culvert at Redcliffe (Australia)

Brazil

Irago peninsula, Japan

Crotty dam, Australia, 1991

Brushes Clough dam, UK in 1993

Choctaw 8A auxiliary spillway (USA) in 2002

Overflow protection systemsReinforced grassMacro-roughness elementsMinimum Energy Loss weir & spillwayConcrete stepped spillwayPrecast concrete blocksGabion (& Reno mattress) structures

Overtopping protection - Minimum Energy Loss weirs

Developments in 1950s in Queensland (Australia)by late Prof Gordon McKay (1913-1989)

Developed to pass large flood flows with minimum affluxin tropical catchments with very-flat bed slope

Chinchilla MEL weir (1973), Q = 850 m3/s, zero afflux

A

A

Earthfill

Concreteslab

Bank top

Section AA

Chinchilla MEL weir (1973), Qdes = 850 m3/s, zero afflux,ICOLD register listed

View from downstream(400 m3/s)

U/s water level

D/s water level

Basic design featuresSmooth flow contraction towards the crestCritical flow conditions at crestConverging chute wallsEnergy dissipation in channel centreline

Clermont weir (1962/63), Qdes = 850 m3/s

MEL spillway inlet designsSwanbank power house (1965)Lake Kurwongbah (850 m3/s, 1958-69)

MEL inlet design allowed extra 0.457 m of water storage

Lake Kurwongbah, Q = 850 m3/s

Swanbank

Prototype experienceOperation for more than 60 years (incl. Q > design flow)

Soundness of design + Little maintenance

There is no better proof of design soundness than successfulprototype experience

Key issue: expert design (Hydraulics expert & Physical modelling)

Major structures1- Sandy Creek MEL weir (Clermont)

1962/63, 850 m3/s, zero afflux2- Chinchilla MEL weir

1973, 860 m3/s, zero affluxlarge dam with international exposure (ICOLD)

3- Lake Kurwongbah (850 m3/s, 1958-69)MEL inlet design allowed extra 0.457 m of water storage

CHANSON, H. (2003). "Minimum Energy Loss Structures in Australia : Historical Development and Experience." Proc. 12th Nat. Eng. Heritage Conf., IEAust., Toowoomba Qld, Australia, N. Sheridan Ed., pp. 22-28 (ISBN 0-646-42775-X).

Embankment overflow concrete stepped spillwaysChoctaw 8A auxiliary spillway in 2002

Salado Creek Dam Site 15R

Developments during 1990s

Numerous applications

Secondary & primary spillways

RCC stepped spillway for a detention basin in west Las Vegas (USACE)

Tongue river dam (USA, 1997)

Ashton dam embankment overflow (USA,1989-1992) : h = 0.6 m, l = 0.9 m, Qmax = 690 m3/s (PMF)

Opuha dam (NZ, 1995-1999) H = 50 m

Melton dam (Australia, 1916/1990s) Q ~ 2,800 m3/s (secondary spillway)

ConstructionConcrete layers (RCC/rollcrete suitability)

Protection layer (in some cases)

Drainage layer beneath steps

Supplemented by drainage holes

Overflow hydraulicsAdequate discharge capacity

Skimming flow regime (Design flow)

Downstream dissipator

Embankment with precast concrete block stepped spillways

Kolymia (or Kolyma) (Courtesy of Prof. Yuri PRAVDIVETS)

Sosnovsky dam (Photograph by Prof. Yuri PRAVDIVETS)Farm dam, 1978. H = 11 m. qw = 3.3 m2/s, So = 0.167. B = 12 m

Russian design under the leadership of P.I. GORDIENKO

Overlapping precast concrete bocks

Primary spillway applications

Klinbeldin

Brushes Clough dam spillway (UK,1859-1991)- wedge shaped concrete blocks (120 kg each)- Chute slope : 18.4�, h = 0.19 m- Inclined downward steps (-5.6�)- Trapezoidal cross-section

(2-m bottom width, 1V:2H sideslope)- Design flow : 3.66 m3/s, Hdam = 26 m- Field tests in 1993

Prototype experiencesSolid record (qw up to 60 m2/s)

High construction standards requiredImportance of drainage layer

Flexibility of spillway channel bed

Hydraulics considerations

* Skimming flow operation

* Straight prismatic cross-sectional channel

* Downstream stilling structure

Bolshevik farm dam (1980), H = 11.5 m. qw = 3.3 m2/s, So = 0.12-0.2, B = 12 m

Volymia experimental earth dam (H=20 m) in the Magadan region (Siberia)

Gabion & Reno mattress protection

Duralie, NSW (Australia)Robina, QLD (Australia)

Porous materialno uplift pressureinteractions between seepage& overflow

Flexible stepped constructiondifferential settlement

Stacked vs lined placementGabion stepped chute

Limited lifetime (5-10 y)gabion resistance to damage by sediments and debris

Design considerations – Overflow protection (all systems)ConstructionStability of earthfill structure is essential� Good construction quality & Simple sound design

Drainage of embankment during overflow

Hydraulic EngineeringDischarge capacity estimate

Downstream dissipation structure

Down-to-earth considerationsHuman interferences

Vandalism (Brushes Clough; Africa)

Prototype experiences: no better proof ofdesign soundness than successful prototype operationNo need to re-invent the ‘wheel’

Summary and Conclusion

Embankments & Earthfill structures�Erodible systems when overtopped

Overtopping protection systemsMinimum Energy Loss weirs & spillwaysConcrete stepped spillwaysPrecast concrete blocksGabion stepped spillwaysMacro-roughness elements

Design and Construction must be soundNo better proof of design soundness than successful prototype operationLearn from successful designs !!!

Look forward seeing you at the5th International Symposium on

Hydraulic Structures25-27June 2014

Full Paper submission deadline: 2 December 2013

THANK YOU

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