Design, Construction and Maintenance of Large...

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Institute for Hydraulic Engineering and Water Resources Management

Professor Horst Cerjak, 19.12.20051

Ljubljana – November - 2008

Design, Construction and Maintenance of Large Dams

Gerald ZenzGraz University of Technology

Contributors - Dam Surveillance Practice from Kaprun Seminar:P.Obernhuber; P.Schöberl; R.Melbinger;




Design, Construction and Maintenance of Large Dams

Dam Safety in AustriaAuthorization ProcedureMultilevel PrincipleObligation of the Owner

Dam Safety EngineerDam Attendant

Safety During Operation / SurveillanceAnnual InspectionFive Year AssessmentAustrian Commission on DamsAspects of Visual Inspections

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Design, Construction and Maintenance

Contributors to Dam Surveillance Practice from Kaprun Seminar:P.Obernhuber; P.Schöberl; R.Melbinger;




MonitoringMeasurementsSurveillanceTesting

EmergencyDraw DownEmergency Plan

Design - ConstructionState of the ArtRegulationsDesign / Concept

AssessmentMaintenance

Dam Safety Seminar – Kaprun - 2005

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Dam Safety

StructuralErosionSlidingFracturing

OperationalFlood ReliefDraw DownReservoir Emptying

Dam and FoundationReservoir and Downstream

Appurtenant StructuresEquipment

FailureAgeingSeepage




Authorization Procedure

Project

Construction

Impounding

Permission Construct

Observation

Permission Operation

Stat

e of

the

Art

Design Documents; Reports; Permission

Operation Surveillance

Certification for permitted operation

Construction Permission

Temp. Operation

Unrestricted Operation

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DAM SAFETY in AUSTRIA

2 Hazard Categories – H≤15m/I≤500.000m3

– H>15m/I>500.000m3 → special check proceduresPublic Safety and Rights of Third Parties protected by the Water LawHigh Safety Level required → Load scenarios with very low probability of

occurrence considered

Periodical „Safety Assessment“ stipulated by the Law

Awareness and Control of Residual Risk (Risk Management)Sound Engineering Judgement EXPERT – and Multilevel PRINCIPLE




Maintenance, i.e. keep the plant in proper and safe condition, according to the license and to the State of the Art

Stick to the operation rules granted by the authority

Appoint a DAM SAFETY ENGINEER and the necessary deputies

Inform the population periodically regarding provisions made forincidents (H>15m, I>2 Mio m3)

Establish and steadily update a Dam file containing all relevantinformation on the dam

Obligation of the Owner

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SAFETY

Des

ign

Con

stru

ctio

n

Emer

genc

y P

repa

redn

ess

Repair/Upgrading

MaintenanceDamage Limitation

Sur

veill

ance

acc.: Fed.Office for Water and Geology/Biel/CH

…in due time!

Sound Engineering Judgement

Competence to decide and

act




Dam Safety during Operation

Surveillance

Continuously Safety checksAnnually Institutional AssessmentEvery five years Institutional Assessment

Design Documents; Permissions; Expert Statements; Instructions to Operate, …

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Continuous Surveillance

Automatic System: Boundary Values

Dam Attendant (DA): Visual, Measurement,Plausibility Check

Dam Safety Engineer(DSI): Plausibility Checks

ProgramVisual Inspection

Measurement Values

Dam File, Reports,Data Base




Annual Inspection

Annual ReportStatement for safe dam

operation

Dam Safety Engineer SurveillanceEvaluation of MeasurementsSafety Assessment

Measurement Reports, Report of Dam Safety Engineer, Geologist, …

CompanyManagementEmployee

AuthorityFederalCentral Government

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Annual Reportwritten by the Dam Safety Engineer

Report:

General: Unusual Events, Data retrievedObservations: Conclusion of Observations

Measurements: Interpretation of behaviourConclusion: Safety Assessment

Attachements:

Inspection Reports, Geology, ..Display of measuremnts




Load scenarios static, dynamic, hydraulic

System Characteristics design, condition, material properties

fissures, cracksappurtenant structuressurveillance system

System Behaviour deformations, seepage, uplift

Stake Holder Interests new arising public safety concerns

State of the Art new criteria, new calculation methods

CHANGES

DAM SAFETY = DYNAMIC PROCESS

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AUTH

ORIT

YD

AM O

WN

ER




Five Year Assessment

Commission of Dams – independent Experts:Visual InspectionAssessment of Measurements, Comparision, Long Term BehaviourState of the ArtSafety Assessment

Written AssessmentPermission to operate,

Additional Requirements

Annual Reports, Five Year ReportDam File

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Austrian COMMISSION on DAMS

Established in the Fed. Min. of Agriculture, Forestry,Environment and Water Management

Experts of all dam related SciencesCheck of the Project in course of the Water Rights Procedure

mandatory if H>15m, I>500.000 m3mandatory if special/unusual methods of design/construction applied, or if difficult foundation conditions

Matters of general importance, fundamental questions (e.g. guidelines)

"Backbone" dam supervision (steady Subcommittee)




Dam related GUIDELINES in AUSTRIA

Stability Assessment for Embankment DamsStability Assessment for Dams under Seismic LoadsDesign of Spillways

Resolutions of the Commission on Dams:– Requirements for the Dam Safety Engineer– Education of Personnel, Dam Safety Courses– Supervision on Minor Dams

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The DAM SAFETY ENGINEER

„Central Switchboard“ for all issues of dam safetynormal operationextraordinary events/incidents

Requirements (DSE+Deputies) Techn. Top Management Dam Expertfamiliar with the plantreliableappropriate Directive Power to take measuresappropriate availability

Comprehensive Liabilities regardg. Dam SupervisionComprehensive Liabilities as to Reporting

Annual Safety Report (Safety assessment)Approval by the Water Authority!!!




Dam Surveillance – Structural Safety Assessment

Attendant

Dam Safety Engineer

Water Authority

Visual Inspection

Annual Inspection

Five Year Assessment

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upstream face (if visible),downstream face,crest cracks

flakingdamages in concretejointswet areassintering

concrete dams

Visual inspection - what ?




inspection galleries cracksflakingdamages in concreteblock jointsconcreting jointsrock (if visible)pipes (grouting, drainage)wet areasleakagepercolation water

concrete dams

visual inspection - what ?

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block joint 7/9 block 19, annual joint

date: 13th October 1999, reservoir level: 1776,38m

Photo documentation - Schlegeis dam




Schlegeis dam, block 2, radial inspection gallerydate: 29th May 2001, reservoir level 1722,29 m

crack leakage

Schlegeis dam, block 9, inspection gallery 3date: 28th May 2002, reservoir level 1723,65 m

Items of Visual Inspection

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surfaceleakages: wet areas

seepagespringssiltationvegetation

deformations: bulgingcrackingslidingsettlements

inspection galleriessee concrete dams

embankment dams





reservoir, slopes sliding, settlementsvegetationriver branchesglaciersdriftwood

downstream dam area springssettlementsslidings

tunnels and caverns flaking of rock or shootcretecracks in rock or shootcreteleakages

hydromechanical equipment damages leakages


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Durlaßboden dam springs

date: 28th August 1985, reservoir level 1404.25 m

down stream dam area




Waag reservoir, date: 12th August 2004

leakage showed by vegetation

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Schlegeis dam, spring in downstream areadate: 14th August 2002, reservoir level 1772,02 m

Eberlaste dam, relief welldate: 9th September 2003, res. level 1115,92 m

Leakages




Bennett Dam, British Columbia

"Sinkhole"

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Birecik dam, date: 26th May 2003repaired bulging

Bürg reservoir, date: 31st May 2001local subsidence of reservoir bank

rip rap shore surrounding

Damages, Deteriorations




Bürg reservoirleft quay

local sliding ofreservoir slope

date: 18th February 1998

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Bürg dam Valle di Lei dam / Switzerland

no danger danger of plugging

Driftwood and spillways




supporting structure

concrete steps

Damages, Deteriorations

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earliest recognition of

deteriorationsdefectsdamagesfailuresabnormal incidents

and

start of necessary measures

visual inspection - why ?




of

hydromechanical equipment

bottom outlets

spillway (if gated)

emergency power supply

voice transmission lines

signal transmission lines

warning and safety devices

measuring equipment

remote monitoring system

testing

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testing - when ?

signaltesting 1 yearpractice 5 years

warning signals1-3 monthmalfunction signal

standby generatorstart 1 month

emergency power supply1 monthlimiting values

1 monthcommunication devices

partial opening1 year

full opening dry1 year

hydro mechanical equipment




emer

genc

yga

te

mai

nga

te

1. emergency gate(no discharge)

Testing scheme for the bottom outlet

2. main gatepartial opening

3. main gatefull opening (dry)

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attention in the river bed !!

even testing of manual drive !!

• date, reservoir level• circumstances• opening value, discharge• time for opening, closing• hydraulic pressure• current consumption

Documentation of Bottom Outlet Testing




Significant reduction of water load (danger)Complete draw down of reservoir Control of reimpoundingOther purposes:

• Sediment flushing• Minimum flow in the river• Flood mitigation (lowering res. level before flood)• River diversion during construction

BOTTOM OUTLETS

SAFETY OPERATIONALPURPOSES

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Equipment

≥ 2 Gates or Valves– Main Control/Service Gate– Standby/Emergency Gate (suitable to cut

off discharge)– Types:

sluice/radial gates, plunger/ hollow jet/butterfly valves

DESIGN (continued)




Flushing(dredging)

SEDIMENT MONITORINGSEDIMENT CONTROL

Depending on catchment area conditions

COMPREHENSIVE REFURBISHMENT/OVER-

HAUL/UPGRADING

Depending on before mentioned assessment

Reservoir empty →scope and schedule of maintenance

works

ASSESSMENT OF STATE INCLUDING UNDER WATER COMPONENTS

10 years

High reservoir levelpartial opening

DISCHARGE TEST1 year

Accessible componentsVISUAL ASSESSMENT OF STRUCTURE

Periodical dam inspection (dam attendant)

Extreme conditions(load / discharge)

(Hydraulic Model Test)

COMPREHENSIVE TESTACCEPTANCE TEST

End of construction /major design alterations

INSPECTION and TESTING

Include check of remote monitoring / control systems!!

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Discharge extreme floods Safety HIGHProbability LOW

Keep reservoir level within allowable limits

SPILLWAYS

MAINLY SAFETY PURPOSES

Types (preferred): ▪ ungated – fixed sill, free flow conditions

▪ gated – gates opened by water pressure

Flood control, flood mitigation




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Availability / Operational Reliability

– Energy Supply redundant! see Bottom Outlets– Reliability/availability of control/monitoring systems

high!Redundant/self monitoring systems

– Access to Control Chamber all over the year– Availability under extreme weather conditions

Ice (heating)Snow

– Provisions to prevent cloggingTrash racks, log boomsControl of sedimentation level at intake

DESIGN

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Fixed rack

Log boom




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Plunge Pool after flood




MAINTENANCE

Weathering, CorrosionAbrasionFissures, cracksLeakage, seepageScourWear of moveable components (gearboxes, seals)Material deficiencies (e.g. in cast metal, welding)Damage to access paths

Discrepancy with STATE of the ART

UPGRADING

Design, Construction and Maintenance of Large...

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