Seismic Safety Evaluation of Concrete Dams. A Nonlinear Behavioral Approach

612 Pages·2014·40.666 MB·English

by  Chong Zhang (Auth.)

C H A P T E R
1
Challenges of High Dam
Construction to Computational
1
Mechanics
Chuhan Zhang
Department of Hydraulic Engineering, Tsinghua University, Beijing
O U T L I N E
1.1 Background 4
1.1.1 Hydropower Development 4
1.1.2 Transbasin WaterTransfer 4
1.1.3 BuildingHighDamsforPowerDevelopmentandWaterTransfer 7
1.2 Building more Bridges betweenComputationalMechanics and
Large Dam Engineering 9
1.2.1 Introduction 9
1.2.2 Key Issues for Safety Evaluation of Large Dams and Power
Plants 10
1.2.2.1 StressandStabilityofDamFoundationsunderNormal
ExternalLoads 10
1.2.2.2 EarthquakeBehaviorofDameFoundationeReservoir
System 12
1.2.2.3 MechanicalPropertiesofMassConcreteforDams 14
1.2.2.4 High-VelocityFlowandEnergyDissipationforHigh
Dams 15
1Computationalmechanics,WCCMVIinconjunctionwithAPCOM’04,September5e10,
2004,Beijing,China.(cid:1)2004TsinghuaUniversityPress&Springer.
SincetheoriginalpaperwaspublishedinWCCMVIin2004,someoftheengineering
projectshavebeencompletedorsomeindexhavebeenchanged,thustheirinformationand
datahavebeenupdatedinthisversion.
SeismicSafetyEvaluationofConcreteDams 3 Copyright(cid:1)2013TsinghuaUniversityPress.Published
http://dx.doi.org/10.1016/B978-0-12-408083-6.00001-5 byElsevierInc.Allrightsreserved.
4 1. CHALLENGESOFHIGHDAMCONSTRUCTIONTOCOMPUTATIONALMECHANICS
1.2.2.5 ScientificandTechnicalProblemsofHydropower
PlantsandUndergroundStructures 17
1.2.2.6 NewlyDevelopedTypesofDam:RollCompacted
ConcreteDamsandConcreteFaceRockfillDams 18
1.3 Research Examples Completed bythe NationalLaboratory of
HighDams and Large Structures at Tsinghua 20
1.3.1 SeismicResponseofArchDamsConsideringCanyonRadiation
Damping and JointOpening 21
1.3.2 Nonlinear FractureAnalysis of Arch Dams 24
1.3.3 Failure Analysis of Arch Dam Foundations 32
1.4 Conclusions 38
References 39
1.1 BACKGROUND
1.1.1 Hydropower Development
Chinaisoneoftherichestcountriesintheworldinhydropowerpotential,
with an exploitable capacity of 540(cid:1)103MW. However, the developed
capacityiscurrentlyis46%,farlowerthanthatoftheUSA,Japan,Canada
andmanyhydropower-richEuropeancountries[1](Fig.1.1).
As hydropower is a green and renewable energy resource, its devel-
opment in China is a crucial strategy for supporting rapid economic
growth, while improving environmental conditions which arebecoming
a serious problem, partly as a result of coal power development. In the
coming three decades, 13 hydropower bases (Fig. 1.2), mainly in south-
west China, including the upper reaches of the Yangtze and Lanchang
Riversandtheirbranches(Jinsha,YalongandDaduRivers),areplanned
to be developed with a total capacity of 278(cid:1)103MW, 51% of the total
hydropower potential of the nation. As an example of cascade develop-
ment, Fig. 1.3 shows the development plan of Yalong River. As the most
developed regions are concentrated in the east Yangtze Delta and south
Pearl River coast, where there is a serious shortage of energy resources,
transmitting hydroelectricity from the west to the east (and south) is an
important task in theyearsahead.
1.1.2 Transbasin Water Transfer
ThequantityofChina’swaterresourceranksnumbersixafterBrazil,
Russia,Canada,theUSAandIndonesia,withanaverageannualrunoff
I.GENERALINTRODUCTION
5
1.1. BACKGROUND
FIGURE1.1 Hydropowerpotentialandcurrentproduction(1999).
of 2800(cid:1)103m3. However, the distributions in space and time season
are extremely uneven. As shown in Fig. 1.4, the runoff in depth varies
from 2000e3000mm in the south to 50e300mm in northern China.
With the rapid growth in the economy, water shortages have become
North main
stream of
Yellow R. Northeast
of China
Upstream
of Yellow R.
YalongR.
Upper steam of
JinshaR.
DaduR. Yangtze R.
Xiangxi Minzhegan
Nu R. Wu R.
LancangR. Hongshui R.
FIGURE1.2 TwelvehydropowerbasesinChina.
I.GENERALINTRODUCTION
6 1. CHALLENGESOFHIGHDAMCONSTRUCTIONTOCOMPUTATIONALMECHANICS
FIGURE1.3 CascadedevelopmentplanoftheYalongRiver.
abottleneckinthesustainabledevelopmentoftheeconomy.TheYellow
River has been subjected to seasonal water interception for years, and
overpumping of groundwater in northern China has caused serious
environmental problems. To alleviate this problem, the central
governmenthasdecidedtotransferwaterfromtheYangtzeRiverbasin
to north and north-western China. As shown in Fig. 1.5, three main
routes starting from the upstream to downstream reaches of the
Yangtze River to the Yellow River and northern China are planned and
construction will start with a total water quantity of 40(cid:1)109m3. The
FIGURE1.4 Meanannualrunoffindepth.
I.GENERALINTRODUCTION
7
1.1. BACKGROUND
FIGURE1.5 Routesofsouth-to-northwatertransferproject.
total cost is around 300 billion RMB. The project is scheduled for
completion in 40 years [2].
1.1.3 Building High Dams for Power Development
and Water Transfer
To accomplish the goals of hydropower development and transbasin
water transfer, construction of a series of high dams up to 250e300m in
heightisbeingplannedorhasstarted.Meanwhile,thereisaneedtobuild
largeundergroundstructureseitherfortheinstallationofpowergenera-
torsorforconveyingwaterfromsouth-westtonorthernChina.Thesehigh
dam projects also serve other purposes, such as flood control and river
navigation. As shown in Fig. 1.2, most of these projects are located in
south-westChinaandpossessthefollowingnaturalconditions(Table1.1):
(1) complicated geological conditions need to be treated carefully to
provide satisfactory foundations and abutments for carrying tens of
million tonnes of thrust loads from the reservoir; (2) seismically active
environmentsandhighseismicityduetoregionaltectonicfaults(Fig.1.6)
in the regions require safety evaluation and analysis of earthquake
behavior of high dams: strengthening measures for high dams to resist
designearthquakes(0.2e0.32g)areusuallynecessary;(3)extraordinarily
large flood overflow through the dams and tunnels causes a serious
problem of energy dissipation: taking the Xiluodu arch dam as an
I.GENERALINTRODUCTION
8 1. CHALLENGESOFHIGHDAMCONSTRUCTIONTOCOMPUTATIONALMECHANICS
TABLE1.1 CharacteristicParametersoftheMainDamsinChina
Dam Design
height Reservoir Installation flood Design
Dam River (m) (108m3) (MW) (m3/s) PGA(g)
Jinping-I YalongR. 305 79.88 3,600 6,900 0.20
Xiaowan LancangR. 294.5 150 4,200 20,700 0.31
Baihetan JinshaR. 277 191 14,000 40,000 0.325
Xiluodu JinshaR. 285.5 92.7 13,860 502,000 0.32
Wudongde JinshaR. 265 74.05 8,700 0.27
Laxiwa YellowR. 250 7.77 4,200 6,000 0.23
Ertan YalongR. 240 58 3,300 23,900 0.20
Goupitan WuR. 232.5 64.54 3,000 27,500 0.116
Longtan HongshuiR. 216.5 299.2 6,300 0.161
Dagangshan DaduR. 210 7.3 2,600 8,320 0.56
Sanxia YangtzeR. 181 450.5 22,500 69,800 0.1
Longyangxia YellowR. 178 274 1,280 7,040 0.237
PGA:peakgroundacceleration.
FIGURE1.6 Peakgroundacceleration(PGA)zonationmapofChina.
I.GENERALINTRODUCTION
9
1.2. BUILDINGMOREBRIDGESBETWEENCOMPUTATIONAL
example,thedesignfloodof50,200m3/smustbeconsideredforoverflow
through spillways and orifices inside the 285.5m high dam and four
abutment tunnels, with a total energy of 95,200MW being dissipated
downstream; (4) two large underground powerhouses, 32m(cid:1)
75.6m(cid:1)444minsize,mustbeexcavatedtoaccommodatethe13,860MW
power generators and auxiliary facilities. Usually, rather high in situ
stresses within the heterogeneous and anisotropic rock media need be
consideredforthestabilityofslidinganddeformationofthesurrounding
rock due to excavation unloading; the above-mentioned engineering
difficulties must be solved to ensuresafety and economy of the projects.
Thegreatchallengespresentedbytheserecord-highdamconstructionsto
damengineersandscientistsprovideawideareaforthedevelopmentand
application of modern computational mechanics and experimental
mechanics,aswellasexperienceindamdesignandconstruction.
1.2 BUILDING MORE BRIDGES BETWEEN
COMPUTATIONAL MECHANICS AND LARGE
DAM ENGINEERING
1.2.1 Introduction
Nowadays,threemaintypesofhighdamareconsideredtobethemost
promisingdamstructuresintheworld,namely,thedoublecurvaturearch
dam, rolled compacted concrete (RCC) dam and concrete facing rockfill
(CFR)dam.Inthepastdecadeworldrecord-heightarchdamseXiaowan,
292mhigh;RCCdamLongtan,216mhighandCFRdamShuibuya,233m
high have been built and the Jinping arch dam, 305m high, will be
completedby2014insouth-westChina.Intheeconomicaldesignandsafety
evaluation of these large dams and hydropower stations, engineering
mechanicsisfacingagreatchallengeinfindingtherightanswerstoprac-
tical problems that are encountered. Continuous, homogeneous and
isotropic media have tobeextended to considerdiscontinuous, heteroge-
neous and anisotropic ones; in many cases material and geometrical
nonlinearitiesorelastoplasticity,damageandfracturemechanicsneedtobe
considered. For considering the randomness of material parameters and
loading input, stochastic and reliabilityanalysismay benecessary;multi-
phase media interaction requires the damereservoirefoundatione
sediment complex system to be taken into account. To study the damage
andruptureprocessofdamandfoundationmaterial,macroemicroscopic
mechanics may be applied. Following the rapid development of digital
computers and numerical algorithms, finite element, finite difference,
boundaryelement,infiniteelementanddiscreteelementmethods,etc.,are
widely used in modeling the damefoundationereservoir system under
I.GENERALINTRODUCTION
10 1. CHALLENGESOFHIGHDAMCONSTRUCTIONTOCOMPUTATIONALMECHANICS
static conditions (reservoir water, temperature, seepage, etc.), dynamic
loadingsandfloodoverflowconditions.
1.2.2 Key Issues for Safety Evaluation of Large Dams
and Power Plants
1.2.2.1 Stress and Stability of Dam Foundations under Normal
External Loads
The methods used to determine arch damefoundation stability have
a long history, from the archecantilever trial load method for dams and
rigidbodylimitequilibriumforfoundationstofiniteelement(FE)analysis
(elasticity or elastoplasticity) (Fig. 1.7). Currently, geological defections
includingfaults,seamsandjointsinrockabutmentscanbeconsideredin
FEanalysisandexperimentaltests(Fig.1.8).Yetdesigncriteriaandspec-
ification in many countries remain at the semi-empiricaletheoretical
stages. For instance, the archecantilever trial load method [3] is still
preferredbyengineersasastresscriterionforarchdams,andthegravity
methodofstrengthofmaterialsisatypicaltoolforanalysisofgravitydams
FIGURE 1.7 Design and research methods for dams. USBR: United States Bureau of
Reclamation;FEM:finiteelementmethod.(References:USBR[3],HowellandJaquith[4],
Londe[5],Clough[6],Cloughetal.[7],Zienkiewicz[8],Kawai[9],Bazantetal.[10],Bazant
[11],Cundall[12],ShiandGoodman[13].)
I.GENERALINTRODUCTION
11
1.2. BUILDINGMOREBRIDGESBETWEENCOMPUTATIONAL
FIGURE 1.8 Experimental model and finite element modeling of Jinping dam and
foundation.
[14].Rigidbodylimitequilibrium[5]iscommonlyusedforcheckingthe
stability of dam foundations and abutments. Although these traditional
methodsgenerallyprovidealowerboundofgrosssafetyfactors,theyfail
togiverealisticstructuralbehaviorsunderworkingconditions.Therefore,
building more bridges with modern computational numerical methods
suchaselastoplasticitymethods,damageandfractureanalysis(including
strain-basedgradientmethods)andeffectivediscontinuousproceduresto
damengineeringisimperative.
The following topics areoutlined for further study:
(cid:129) simulationofstructuralbehaviorofthecompleteprocessstartingfrom
concrete pouring to normal operation of dams
(cid:129) modeling of elastoplasticity deformation and stability conditions for
damefoundationsystems
(cid:129) stability against wedgesliding of arch dam foundations
(cid:129) stability against upward slidingof archdamabutments
(cid:129) couplingofseepageflowwithstressfieldsinthefoundationandeffects
on dameabutmentstability
(cid:129) thermal stresses due to internal hydration heatand environmental
temperatures
(cid:129) fractureprediction at the upstreamheel,singularity, meshsensitivity
andfractureprocessof arch dams
(cid:129) theory andmethods of shape optimization for arch dams [15]
(cid:129) randomness of materialparametersand reliability analysisfordams
(cid:129) couplingofcontinuumanddiscontinuummediaforsimulationofthe
rockmass of dam foundations
(cid:129) isotropicand anisotropic behavior, damage localizationand strain-
gradientmodelsforconcrete andjointedrocks
(cid:129) back-analysis methods for rockparameters
(cid:129) discontinuous mechanics for ruptureanalysis:simulation offailure
processof damefoundationsystems.
I.GENERALINTRODUCTION
12 1. CHALLENGESOFHIGHDAMCONSTRUCTIONTOCOMPUTATIONALMECHANICS
1.2.2.2 Earthquake Behavior of DameFoundationeReservoir
System
Theimportanceofseismicsafetyevaluationofexistinghighdamsand
dams to be built is well recognized owing to the catastrophic conse-
quences of dam failure during strong earthquakes. The prototype
performance of concrete dams during earthquakes was discussed by
Hansen and Roehm [16]. Among the earthquake damage to high dams,
the following accidents may be noted: severe damage to the Lower San
FernandodamandconstructionjointopeninginthePacoimaarchdamin
the 1971 San Fernando earthquake [17]; large-scale slope slide in the
Miyun Baihe main dam (China) near Beijing during the 1976 Tangshan
earthquake [18]; severe cracking of the Hsingfengjiang dam [19] and
Koynadam[20]duetoreservoir-triggeredearthquakesin1962and1967,
respectively; and a rupture and movement of 8m in the Shih-Kang
concrete dam spillway during the Chi-Chi earthquake in 1999 (Taiwan)
(Fig. 1.9). Many other examples of cracking and damage during strong
earthquakes have also been reported from other countries, including
Japan (1995, 2000), Iran (1990) and Mexico (1985) [21].
Although more precise knowledge and sophisticated numerical tools
forearthquakeanalysiswithrespecttolargedamsappeartobeavailable,
realisticearthquakebehavioranddamagemechanismsoflargedamsare
still far from clear [22,23]. The current state of practice is that the design
maximumcredibleearthquake(MCE)isrepresentedbythepeakground
acceleration (PGA) and corresponding response spectrum, while the
safety check for dams is controlled by the maximum principal tensile
stressesusingalinearelasticapproach.However,itisreportedthatpeak
accelerations of over 2g at the crest of the Pacoima archdam during the
1994 Northridge (USA) earthquake and 2.1g on the crest of the Kasho
FIGURE1.9 RuptureoftheShih-KangconcretedamduringtheChi-Chiearthquake.
I.GENERALINTRODUCTION