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FOUNDATION TREATMENT OF FOUNDATION TREATMENT OF CONCRETE DAMS CONCRETE DAMS

Dr. V.M.SHARMA FNAEDr. V.M.SHARMA FNAEDirector AIMIL Ltd.Director AIMIL Ltd.

Seminar at Institute of Science, Seminar at Institute of Science, Bangalore, 24Bangalore, 24thth March 2009 March 2009

INTRODUCTIONINTRODUCTION

DAMS ARE HIGH COST STRUCTURES DAMS ARE HIGH COST STRUCTURES DAMS ARE ALSO HIGH RISK STRUCTURESDAMS ARE ALSO HIGH RISK STRUCTURESFAILURES CAN BE CATASTROPHICFAILURES CAN BE CATASTROPHICOUT OF ALL THE HIGH DAMS (>15m height) OUT OF ALL THE HIGH DAMS (>15m height) SURVEYED BY ICOLDSURVEYED BY ICOLDTOTAL NUMBER IS NEARLY 15,000 TOTAL NUMBER IS NEARLY 15,000 ABOUT 7.5% HAVE SUFFERED DETERIORATIONABOUT 7.5% HAVE SUFFERED DETERIORATIONABOUT 0.7%HAVE FAILEDABOUT 0.7%HAVE FAILED

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PERCENTAGE TYPE OF DAMS CONSTRUCTEDPERCENTAGE TYPE OF DAMS CONSTRUCTED

OUT OF ALL DAMS EARTHFILL DAMS 62.6OUT OF ALL DAMS EARTHFILL DAMS 62.6ROCKFILL DAMS ROCKFILL DAMS 4.804.80

6767.4.4

CONCRETE DAMS GRAVITY 25.1CONCRETE DAMS GRAVITY 25.1BUTRESS 1.8BUTRESS 1.8ARCH 4.8ARCH 4.8

MULTIMULTI--ARCH ARCH 0.90.9332.62.6

PERCENTAGE FAILURE OF CONCRETE PERCENTAGE FAILURE OF CONCRETE DAMS DAMS

OUT OF TOTAL CONCRETE DAM OUT OF TOTAL CONCRETE DAM FAILURESFAILURES

ARCH DAMS 0.7%ARCH DAMS 0.7%BUTTRESS DAMS 2.6%BUTTRESS DAMS 2.6%GRAVITY DAMS 0.3% GRAVITY DAMS 0.3%

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CAUSES OF FAILURESCAUSES OF FAILURES

OVERTOPPING 29%OVERTOPPING 29%PIPING & SEEPAGE 0%PIPING & SEEPAGE 0%FOUNDATION 53%FOUNDATION 53%OTHERS 18%OTHERS 18%

THE INDIAN SCENETHE INDIAN SCENE

MORE THAN 4000 LARGE DAMS IN INDIAMORE THAN 4000 LARGE DAMS IN INDIA

SEVERAL HUNDREDS ARE UNDER SEVERAL HUNDREDS ARE UNDER CONSTRUCTION MOSTLY IN HIMALAYASCONSTRUCTION MOSTLY IN HIMALAYAS

EVERY PROJECT HAS COMPONENTS OF EVERY PROJECT HAS COMPONENTS OF CONCRETE GRAVITY STRUCTURES CONCRETE GRAVITY STRUCTURES

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GEOLOGICAL CONCERNSGEOLOGICAL CONCERNS

PLANAR FEATURESPLANAR FEATURESThin Shear or Weak Planar ZonesThin Shear or Weak Planar ZonesWeak JointsWeak JointsFaults and Fault ZonesFaults and Fault Zones

ZONAL FEATURESZONAL FEATURESSolution CavitiesSolution CavitiesWeathered ZonesWeathered ZonesBuried ChannelsBuried Channels

THIN SHEAR OR WEAK PLANAR ZONESTHIN SHEAR OR WEAK PLANAR ZONES

COMMONLY IN SEDIMENTARY AND COMMONLY IN SEDIMENTARY AND METAMORPHIC ROCKSMETAMORPHIC ROCKSPARALLEL TO FOLIATIONPARALLEL TO FOLIATIONTHIN THIN –– VARIES FROM 5mm TO 100mmVARIES FROM 5mm TO 100mmCONTAINS GOUGE WHICH IS MICACEOUSCONTAINS GOUGE WHICH IS MICACEOUSLOW SHEAR STRENGTH APPROACHING LOW SHEAR STRENGTH APPROACHING RESIDUAL STRENGTH RESIDUAL STRENGTH

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JOINTED FAULTED ROCK AT A DAM SITEJOINTED FAULTED ROCK AT A DAM SITE

ANOTHER VIEW OF THE SAME SITEANOTHER VIEW OF THE SAME SITE

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WEAK JOINTSWEAK JOINTS

ALMOST ALL ROCK MASSES ARE JOINTEDALMOST ALL ROCK MASSES ARE JOINTEDTHREE OR MORE JOINT SETSTHREE OR MORE JOINT SETSSOME ARE FILLED WITH CLAY OR SOME ARE FILLED WITH CLAY OR WEATHERED MATERIALWEATHERED MATERIALSOME JOINTS ARE SLICKENSOME JOINTS ARE SLICKEN--SIDED SIDED REDUCING THEIR SHEAR STRENGTHREDUCING THEIR SHEAR STRENGTHIN HIMALAYAS, WE FIND LARGE RELIEF IN HIMALAYAS, WE FIND LARGE RELIEF JOINTS NEAR ABUTMENTS (>300 mm)JOINTS NEAR ABUTMENTS (>300 mm)

CASE OF TIGRA DAM CASE OF TIGRA DAM –– indianindian cotributioncotribution

100 FT. HIGH DAM ACROSS RIVER SANK, FOR 100 FT. HIGH DAM ACROSS RIVER SANK, FOR IRRIGATION NOW FOR WATER SUPPLY OF GWALIORIRRIGATION NOW FOR WATER SUPPLY OF GWALIORBUILT IN 1913BUILT IN 1913--1917 ON MASSIVE ROCK FOUNDATION1917 ON MASSIVE ROCK FOUNDATION

FAILED IN FIRST FILLING ; BURST IN 800 ft LENGTHFAILED IN FIRST FILLING ; BURST IN 800 ft LENGTHBROKEN DAM STANDS DOWNSTREAM EVEN TODAYBROKEN DAM STANDS DOWNSTREAM EVEN TODAYSOME PARTS MOVED SEVERAL KILOMETERSSOME PARTS MOVED SEVERAL KILOMETERSEARLIER EXPERIENCE WAS WITH GRANITE BASALT etc.EARLIER EXPERIENCE WAS WITH GRANITE BASALT etc.12 YEARS OF INVESTIGATIONS REVEALED THAT 12 YEARS OF INVESTIGATIONS REVEALED THAT SANDSTONE WITH HORIZONTAL SEAMS LED TO UPLIFTSANDSTONE WITH HORIZONTAL SEAMS LED TO UPLIFTA CLAY BLANKET AND A TRENCH UPSTREAM COVERED A CLAY BLANKET AND A TRENCH UPSTREAM COVERED WITH QUARRIED STONE WAS PROVIDED IN 1929. OK . WITH QUARRIED STONE WAS PROVIDED IN 1929. OK .

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DAM AT BHOJPUR DAM AT BHOJPUR –– indianindian contributioncontribution

AN EARTH DAM WAS BUILT BY RAJA BHOJ ACROSS AN EARTH DAM WAS BUILT BY RAJA BHOJ ACROSS RIVER BETWA AT BHOJPUR IN 12RIVER BETWA AT BHOJPUR IN 12THTH CENTURYCENTURYTHE DAM ABUTS A ROCKY HILLOCK WHERE A CUT WAS THE DAM ABUTS A ROCKY HILLOCK WHERE A CUT WAS PROVIDED TO SPILL EXTRA FLOODS PROVIDED TO SPILL EXTRA FLOODS TODAY ONLY A BREACHED PORTION REMAINS TODAY ONLY A BREACHED PORTION REMAINS IN SUBSEQUENT YEARS, A NAWAB RULER BREACHED IN SUBSEQUENT YEARS, A NAWAB RULER BREACHED INTENTIONALLY TO GROW WHEAT IN THE RESERVOIR INTENTIONALLY TO GROW WHEAT IN THE RESERVOIR AREA TO WARD OFF A SEVERE FAMINE AREA TO WARD OFF A SEVERE FAMINE SPILLWAY IS AN INTEGRAL PART OF DAMS TODAY SPILLWAY IS AN INTEGRAL PART OF DAMS TODAY

FAULTSFAULTS

GENERALLY PLANAR BUT EXTENDING GENERALLY PLANAR BUT EXTENDING OVER LARGE DISTANCESOVER LARGE DISTANCESORIENTATION IS INDEPENDENT OF ORIENTATION IS INDEPENDENT OF BEDDING OR FOLIATIONBEDDING OR FOLIATIONTHICKNESS FEW mm TO SEVERAL mTHICKNESS FEW mm TO SEVERAL mADJOINING ROCK IS HIGHLY FRACTUREDADJOINING ROCK IS HIGHLY FRACTUREDIF IT CROSSES THE STRUCTURE, A CUTIF IT CROSSES THE STRUCTURE, A CUT--OFF MAY BE REQUIRED OFF MAY BE REQUIRED

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PROBLEMS PROBLEMS –– HEAVY OVERBURDEN AND BURIED HEAVY OVERBURDEN AND BURIED CHANNELSCHANNELS

SOLUTION CAVITIES SOLUTION CAVITIES -- LIMESTONELIMESTONE

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SHEAR ZONES, FOLDS AND FAULTS SHEAR ZONES, FOLDS AND FAULTS

TREATMENT CARRIED OUT TREATMENT CARRIED OUT CONVENTIONALLYCONVENTIONALLY

EXCAVATE WEAK PORTION AND FILL EXCAVATE WEAK PORTION AND FILL BACK WITH CONCRETEBACK WITH CONCRETE

d = 0.002 d = 0.002 bHbH + 5 for H > 150 ft.+ 5 for H > 150 ft.d = 0.3 b + 5 for H < 150 ft.d = 0.3 b + 5 for H < 150 ft.

where H = height of the dam where H = height of the dam b = width of the weak zone b = width of the weak zone d = depth of excavation weak zoned = depth of excavation weak zone

for clay gouge d > 0.1 H for clay gouge d > 0.1 H

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PROPERTIES REQUIRED FOR DESIGNPROPERTIES REQUIRED FOR DESIGN

MODULUS OF DEFORMATION MODULUS OF DEFORMATION Plate Loading Test inside DriftPlate Loading Test inside DriftPlate Jacking Test with Borehole ExPlate Jacking Test with Borehole ExGoodman Jack inside BoreholesGoodman Jack inside BoreholesDilatometersDilatometersBack Analysis Back Analysis -- Numerical Modeling Numerical Modeling Empirical Relations Empirical Relations –– Barton’s Q orBarton’s Q or

Bieniawski’sBieniawski’s RMR based RMR based

PLATE LOADING TESTPLATE LOADING TEST

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PLATE JACKING TEST WITH BOREHOLE PLATE JACKING TEST WITH BOREHOLE EXTENSOMETERS EXTENSOMETERS

MODULUS OF DEFORMATION FROM RMR AND QMODULUS OF DEFORMATION FROM RMR AND Q

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COMPETENT ROCK DAMAGED DUE TO COMPETENT ROCK DAMAGED DUE TO BLASTINGBLASTING

PRESSURE DEFORMATION PRESSURE DEFORMATION -- SOFT ROCKSOFT ROCK

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STRONG COMPETENT ROCKSTRONG COMPETENT ROCK

STRENGTH OF ROCK MASSSTRENGTH OF ROCK MASS

DIFFICULT TO DETERMINE IN THE FIELD, HENCE DIFFICULT TO DETERMINE IN THE FIELD, HENCE EMPIRICAL RELATIONS ARE USEDEMPIRICAL RELATIONS ARE USEDGENERALIZED HOEK AND BROWN FAILURE CRITERION GENERALIZED HOEK AND BROWN FAILURE CRITERION

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ININ--SITU TRIAXIAL TEST FOR ROCK MASSSITU TRIAXIAL TEST FOR ROCK MASS

ROCK STRENGTH TEST INROCK STRENGTH TEST IN--SITUSITU

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MODULUS BY EXTRA LARGE FLAT JACKSMODULUS BY EXTRA LARGE FLAT JACKS

FOR SHEARING SLIDING STABILITYFOR SHEARING SLIDING STABILITY

SHEAR STRENGTH OF ROCK JOINTSSHEAR STRENGTH OF ROCK JOINTSSHEAR STRENGTH OF CONC INTERFACESHEAR STRENGTH OF CONC INTERFACESHEAR STRENGTH OF JOINTS WITH CLAYSHEAR STRENGTH OF JOINTS WITH CLAYKnKn –– NORMAL STIFFNESS OF JOINTSNORMAL STIFFNESS OF JOINTSKs Ks –– SHEAR STIFFNESS OF JOINTSSHEAR STIFFNESS OF JOINTSFIELD SHEAR TESTSFIELD SHEAR TESTSPORTABLE SHEAR TEST APPARATUS PORTABLE SHEAR TEST APPARATUS

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ININ--SITU SHEAR TESTSITU SHEAR TEST

SHEAR TEST ON CLAY SEAMSSHEAR TEST ON CLAY SEAMS

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PORTABLE SHEAR TEST APPARATUSPORTABLE SHEAR TEST APPARATUS

SCHEMATIC DIRECT SHEAR TESTSCHEMATIC DIRECT SHEAR TEST

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DESIGN CONSIDERATIONSDESIGN CONSIDERATIONS

STABILITY AGAINST OVERTURNINGSTABILITY AGAINST OVERTURNINGSTABILITY AGAINST SHEARING SLIDINGSTABILITY AGAINST SHEARING SLIDINGMAX. PRINCIPAL STRESSES IN LIMITSMAX. PRINCIPAL STRESSES IN LIMITSEFFECT OF TENSILE STRESSES & CRACKSEFFECT OF TENSILE STRESSES & CRACKSPERMEABILITY PERMEABILITY –– UPLIFT CRITERIONUPLIFT CRITERIONDEFORMABILITY WITHIN LIMITSDEFORMABILITY WITHIN LIMITSGROUTABILITY GROUTABILITY

CASE STUDY 1 CASE STUDY 1 –– SALAL DAM (J&K)SALAL DAM (J&K)

RIVER CHENAB FORMS A ‘S’ LOOP WHICH RIVER CHENAB FORMS A ‘S’ LOOP WHICH IS EXPLOITED FOR HYDROPOWERIS EXPLOITED FOR HYDROPOWERIT IS A DOLOMITE TERRAINIT IS A DOLOMITE TERRAINWELL DEFINED BEDDING PLANESWELL DEFINED BEDDING PLANESHEAVILY SHEARED HEAVILY SHEARED SHEAR ZONES / PLANES PARALLEL TO SHEAR ZONES / PLANES PARALLEL TO BEDDING PLANE DIPPING UPSTREAMBEDDING PLANE DIPPING UPSTREAMCROSS SHEAR SEAMS DISCOVERED LATECROSS SHEAR SEAMS DISCOVERED LATE

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THE PROBLEMTHE PROBLEM

THE MAIN RIVER WAS BLOCKED WITH THE MAIN RIVER WAS BLOCKED WITH AN EARTH & ROCKFILL DAMAN EARTH & ROCKFILL DAMRIDGE CONSIDERED NATURAL SPILLWAYRIDGE CONSIDERED NATURAL SPILLWAYINITIAL INVESTIGATION SHOWED THE INITIAL INVESTIGATION SHOWED THE SHEAR SEAMS TO BE DIPPING UPSTREAMSHEAR SEAMS TO BE DIPPING UPSTREAMDETAILED INVESTIGATION SHOWED DETAILED INVESTIGATION SHOWED CROSS SHEAR SEAMS CAUSING SLIDINGCROSS SHEAR SEAMS CAUSING SLIDINGACCEPABLE S.F.F. WAS LOWERED ACCEPABLE S.F.F. WAS LOWERED

LAYOUT PLAN OF SALAL H.E. PROJECTLAYOUT PLAN OF SALAL H.E. PROJECT

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CONCRETE DAM PLAN & ELEVATIONCONCRETE DAM PLAN & ELEVATION

MAXIMUM SECTION OF SPILLWAYMAXIMUM SECTION OF SPILLWAY

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SALAL DAM SPILLWAY & POWER DAMSALAL DAM SPILLWAY & POWER DAM

SALAL DAM SPILLWAYSALAL DAM SPILLWAY

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ON THE BASIS OF ON THE BASIS OF

LARGE NUMBER OF FIELD SHEAR TESTSLARGE NUMBER OF FIELD SHEAR TESTSMEASURED ROUGHNESS ALONG DOWN MEASURED ROUGHNESS ALONG DOWN STREAM DIPPING SHEAR SEAMSSTREAM DIPPING SHEAR SEAMSTHERE WERE NO SIGNIFICANT VERTICAL THERE WERE NO SIGNIFICANT VERTICAL JOINTS IN THE RIDGEJOINTS IN THE RIDGESEAM MATERIAL WAS ROCK GRIT & POWDER SEAM MATERIAL WAS ROCK GRIT & POWDER CONCRETING ON THE UPSTREAM SIDE CONCRETING ON THE UPSTREAM SIDE DRAINAGE ON THE DOWNSTREAM SIDEDRAINAGE ON THE DOWNSTREAM SIDEMATTERS COMPLICATED BY TREATYMATTERS COMPLICATED BY TREATY

SECOND CASE SECOND CASE –– INDIRASAGAR DAMINDIRASAGAR DAM

LOCATED 10 km AWAY FROM PUNASA LOCATED 10 km AWAY FROM PUNASA VILLAGE IN KHANDWA DISTRICTVILLAGE IN KHANDWA DISTRICTHAS A CREST LENGTH OF 653 mHAS A CREST LENGTH OF 653 m92 m HIGH CONCRETE GRAVITY DAM92 m HIGH CONCRETE GRAVITY DAMSLIGHTLY CURVED IN PLANSLIGHTLY CURVED IN PLANSURFACE POWER HOUSE WITH 8 UNITS SURFACE POWER HOUSE WITH 8 UNITS OF 125 MW EACHOF 125 MW EACH

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AN AERIAL VIEW OF INDIRASAGAR DAMAN AERIAL VIEW OF INDIRASAGAR DAM

THE PROBLEMTHE PROBLEM

NEARLY VERTICAL SHEAR SEAM NEARLY VERTICAL SHEAR SEAM RUNNING UPSTREAM TO DOWNSTREAMRUNNING UPSTREAM TO DOWNSTREAMNARROW WIDTH NARROW WIDTH –– SHASTA FORMULA SHASTA FORMULA MODULUS VALUES DIFFICULT TO GETMODULUS VALUES DIFFICULT TO GETPARAMETRIC STUDIES WERE DONE WITHPARAMETRIC STUDIES WERE DONE WITH

i) i) moduliimodulii rock : rock : szoneszone :: 100 : 1:: 100 : 1ii) ii) moduliimodulii rock : rock : szoneszone :: 10 : 1:: 10 : 1iii) iii) moduliimodulii rock : rock : szoneszone :: 5 : 1 :: 5 : 1

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SHEAR ZONE SHEAR ZONE –– INDIRASAGAR DAMINDIRASAGAR DAM

MODULUS OF ROCK : SHEAR ZONE :: 100:1 MODULUS OF ROCK : SHEAR ZONE :: 100:1

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MODULUS ROCK:SHEAR ZONE::10:1MODULUS ROCK:SHEAR ZONE::10:1

MODULUS ROCK : SHEAR ZONE :: 5:1MODULUS ROCK : SHEAR ZONE :: 5:1

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THIRD CASE THIRD CASE -- OMKARESHWAR DAM (MP)OMKARESHWAR DAM (MP)

LOCATED 80 KM FROM INDORE, 40 KM LOCATED 80 KM FROM INDORE, 40 KM DOWNSTREAM OF INDIRASAGARDOWNSTREAM OF INDIRASAGAR949 m LONG CONCRETE GRAVITY DAM949 m LONG CONCRETE GRAVITY DAM53 m HIGH 53 m HIGH HAS A SURFACE POWERHOUSE WITH 8 HAS A SURFACE POWERHOUSE WITH 8 UNITS OF 65 MW EACH UNITS OF 65 MW EACH

OMKARESHWAR DAM (MP)OMKARESHWAR DAM (MP)

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THE PROBLEMTHE PROBLEM

FOUNDATIONS HAVING HORIZONTALLY FOUNDATIONS HAVING HORIZONTALLY STRATIFIED FORMATIONSSTRATIFIED FORMATIONSSHEARING SLIDING STABILTY IN DOUBTSHEARING SLIDING STABILTY IN DOUBTBLOCK SHEAR TESTS WERE CONDUCTEDBLOCK SHEAR TESTS WERE CONDUCTEDANALYSIS SHOWED SLIDING FAILUREANALYSIS SHOWED SLIDING FAILUREA SHEAR KEY IN DOWNSTREAM AREA A SHEAR KEY IN DOWNSTREAM AREA WAS PROPOSED AND ANALYZEDWAS PROPOSED AND ANALYZEDKnKn AND Ks WERE DETERMINED BY BACK AND Ks WERE DETERMINED BY BACK ANALYSIS OF BLOCK SHEAR TESTS ANALYSIS OF BLOCK SHEAR TESTS

OMKARESHWAR DAM WITHOUT KEYOMKARESHWAR DAM WITHOUT KEY

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PRINCIPAL STRESSES max tension 1.2 PRINCIPAL STRESSES max tension 1.2 MPaMPa

NO E’QUAKE NO E’QUAKE –– max shear max shear displdispl. 1.1 mm. 1.1 mm

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WITH E’QUAKE max tension 1.53 WITH E’QUAKE max tension 1.53 MPaMPa

SHEAR DISPLACEMENT max 5.1 mmSHEAR DISPLACEMENT max 5.1 mm

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DAM SECTION WITH A SHEAR KEYDAM SECTION WITH A SHEAR KEY

RES FULL NO E’QUAKE max tension 1.17 MP RES FULL NO E’QUAKE max tension 1.17 MP

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NO E’QUAKE NO E’QUAKE –– max shear max shear displdispl. 0.74 mm. 0.74 mm

WITH E’QUAKE WITH E’QUAKE –– max tension 1.3 max tension 1.3 MPaMPa

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WITH E’QUAKE WITH E’QUAKE –– max shear max shear displdispl. 2.3 mm. 2.3 mm

SIMULATION OF BLOCK SHEAR TESTSIMULATION OF BLOCK SHEAR TEST

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SHEAR STRESS VS. SHEAR DISPLACEMENTSHEAR STRESS VS. SHEAR DISPLACEMENT

FIELD BLOCK SHEAR TEST RESULTSFIELD BLOCK SHEAR TEST RESULTS

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RESULTSRESULTS

SlSl No Full Reservoir Full ReservoNo Full Reservoir Full Reservoirir

No Earthquake with No Earthquake with E’quakeE’quake(key/no key) (key/no k(key/no key) (key/no key) ey)

1.1. Max. Compressive 2.3/2.38 3.012/3.096Max. Compressive 2.3/2.38 3.012/3.096

2.2. Tensile stresses 1.2/1.17 1.53/1.31Tensile stresses 1.2/1.17 1.53/1.31

3.3. Displacement 1.10/0.74 5.14/2.33 Displacement 1.10/0.74 5.14/2.33

GREY AREAS WHERE MORE WORK IS GREY AREAS WHERE MORE WORK IS REQUIREDREQUIRED

‘‘STRENGTHS’ OF ROCK MASS size effectsSTRENGTHS’ OF ROCK MASS size effectsFLOW THROUGH JOINTED ROCKS FLOW THROUGH JOINTED ROCKS

through fissures, Darcy’s law not applicable through fissures, Darcy’s law not applicable UPLIFT FORCES; CASE OF TIGRA DAMUPLIFT FORCES; CASE OF TIGRA DAMINPUT PARAMETERS FOR MODELLINGINPUT PARAMETERS FOR MODELLINGQUANTIFYING THE EFFECT OF DRAINAGEQUANTIFYING THE EFFECT OF DRAINAGEEFFECT OF BLOCK SIZE ON SHEAR TESTS EFFECT OF BLOCK SIZE ON SHEAR TESTS

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THANK YOU VERY MUCHTHANK YOU VERY MUCH

CONTACT NUMBER & MAILCONTACT NUMBER & MAIL98100 1816798100 18167

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