examination report - sh dam

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1.CONTROL NUMBER 2.SUBJECT CLASSIFICATION (695)IBLIOGRAPHIC DATA SHEEi ? -0 n. TV 3.TITLEDS ITLE 24 0) Q*4. 'PERSONAL A flORS (100)

5. CORPORATE AUTHORS (101)

"6. DOCUMENT DATE (1!0) cr 7. NUMBER OF PAGES (120) - - ARC NUMBER ( 170)9. REFERENCE ORGANIZATION (130)10. SUPPLEMENTARY NOTES (500)

11. ABSTRACT (950)

12. DESCRIPTORS (I20) 13. PROJECT NUMBER (150)

14. CONTRACT NO.(14) 15 CONTRACf ~~~_ _TYPE (140.. 1.co~~o~o4c o", , 16. TYPE OF DOCUMENT (160)

AMD 590-7 (10.79)


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Examination Reportof Civil WorksKarnaphuli Third UnitKaptai, Bangladesh

Prepared byUNITED STATESDEPARTMENT OF THE INTERIORBureau of Reclamat ion1981


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UNITED STATES OF AMERICAAgency 'for International 'Development

Civil Works Repair.- Karnaphuli Third UnitKaptai, Bangladesh

PIO/T.No. 388-0018'3-10300

EXAMINATION: REPORT OF CIVIL WORKS1981'

Prepared, byRichardW.. Kramer ,- Asst'. Chief, Dams BranchRalph'0. Atkinson, Head, Concrete Dams, Spillwaysan d Out let Works Section

UNITED STATES DEPARTMENT OF THE INTERIORBureau of ReclamationEngineering and Research CenterDenver, Colorado
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ACKNOWLEDGMENTS

Our stay at Kaptai was very enjoyable; our work schedule very full and thecooperation given us by the personnel of the Karnaphuli Hydro Station fo r ourmany requests was most outstanding. We wish to express our sincere apprecia-.tion to Messrs. A.F.M. Moeenul Islam, Manager, and A.K.M. Mukaddas, DeputyManager and Plant Engineer, and their staffs for their help and hospitality.The support and arrangements of the USAID offices in Dacca and Chittagong andthe Power Development Board were appreciated and instrumental incompleting'the work on the tight schedule.


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CONTENTS PageI Reference . . ... . . . . . . . . . . . . . . . . . . . 2

Summary ..n..p.... Op. .... . ... . . . . . . . .3References . . . . . . . . . . .. ... . . . . . . ..

Gener al ." in.. . . .. .. 3Chutei lwa .......... ........ . .. * * * . . . .. . . 3Hydrologyan Spliwy Operat .. . . . . . . . . . . . . 3Do iwnram.hannel . . . . . . . . . . . .. . . . . . . . . 3nae Structure . . . . ..... . . . . . . . .. ..... 4Stilling Basin So . . . . . . . . . .6 . . 1Downstream o . . . . . . . . ... ........GateowruFcites . . . . . . .* . . . *. . 4ight Bank Stability . . . . . . 8IV. Power Facilities .. . . . . 1

General W . . . . . . . . . . . . .. . . . . . . . . . 91Dr.inag allry . ..................... 18Powerpl an g at . . . . . .. . . . 1ad Slop . . ... .. . .... .ccesntake Rontruture.. . . . . .. . . . . . ..... . . 12Tailrace Channel Slopes .. . .. . . . . . .. . 1Slope Upstream of Power .1981.Me:Drainage Gallery .Access Road Slope in 12

V. Cargo Transfer System . . . . . . .e..13VIS Outlet Works . .4

General . . . . .2....CnrlBuilding'and'Access Shaft. 1414Downstream Diversion Tunnel ........... 14

AppendixMinutes of September 22, 1981' MeetingPhotographsSpillway DrawingsTechnical Specifications and Standards-Scope of Work LMemorandum, October 22,.1981


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I. INTRODUCTIONThis report of the examination of Civil works at Karnaphuli Hydro Station isbased upon an onsite inspection by Messrs. Ralph 0. Atkinson and Richard W.Kramer-0 during the period September 22-26, 1981, discussions with personnelof USAID/Dacca and Bangladesh PBD (Power Development Board), Dacca, andreview of the material listed in th e section "References".

SummaryThe U.S. Agency for International Development Mission to Bangladesh(USAIU/Dacca) requested the services of the Bureau of Reclamation toreview and comment on a scope of work prepared fo r the repair and rehabilitation of the civil works of the Karnaphuli hydropower generatingplant and dam located at Kaptai on the Karnaphuli River in Bangladesh.Our examination of the civil works indicated no serious problems. Theproblems encountered, both reported and observed, are not uncommon toprojects 20 years of age. This report contains our recommendations ofmaintenance and/or modifications required to solve the existing problems.Some of th e problems should be remedied as soon as climate, funds, andfacilities permit, while other repairs or modifications may be delayed fora reasonable amount of time.The reported horizontal "cracks" in the spillway chute were determined tobe construction joints between the original concrete and the concreteplaced for the reconstruction after the 1961 spillway chute failure. Wehave recommended a core drilling program through th e spillway chuteconcrete to establish the present conditions of the concrete and theinterface between the concrete and foundation.In addition, it is important that the existing spillway design be evaluated for the hydraulic and structural conditions established by an updatedIDF (inflow design flood) and the core drilling program.The project's operation and maintenance of the structures have beenoutstanding. Instrumentation readings and data collection have been,excellent. However, the instrumentation data have not been plotted-whichmakes it difficult to follow the performance of the dam and to identifydeveloping problems.Our recommended "Scope of Work" for the civil works is included in theappendix to this report. It is based upon our field examination of theworks and review of all available information. We discussed methods forimplementing the necessary repairs with USAID/Dacca before leavingBangladesh.

1/ Ralph 0. Atkinson - Head, Concrete Dams, Spillways and Outlets Section;Richard W. Kramer - Assistant Chief, Dams Branch; Bureau of Reclamation,Engineering and Research Center, Denver, Colorado, U.S.A.


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References1. Telex Secstate Wash. to Mr. Joseph A. Cutschall, Code 2000 BUREC,Civil Repair at Karnaphuli Hydrostation, August 31, 1981.2. Memo to Addl. Chief Engineer, PDB, Dacca, from A.F.M. MoeenulIslam, Manager (Power) Karnaphuli Hydro Station, Work of repair andrehabilitation of power house and allied features of Karnaphuli HydroStation, Kaptai April 1, 1981.3. Minutes of the meeting held on September 22, 1981, between PDB,USBR, and USAID, inMr. Islam's office, Manager (Power),Karnaphul: Hydio Station (Inappendix to this report).4. Report on Civil Works Repair Requirements, Karnaphuli Hydro Project,Contract No. AID/OTR-C-1646, Chas. T. Main International.Inc.,Boston, Massachusetts.5. Inspection and Engineering Appraisal of Karnafuli Hydro StaionUnits No. I and 2, Contract No. AID/OTR-C-1646, Chas. T. Main International Inc., Boston, Massachusetts.6. Rahman, Mohammad A., "Damage to Karnafuli Dam spillway", ASCEJournal of the Hydraulics Division, HY 12, December 1972.7. Discussions of Mohammad A. Rahman's paper, "Damage to Karnafuli DamSpillway," ASCE Journal of Hydraulics Divibion HY11, November, 1973.

a. by James L. Sherardb. by Alvin J. Peterkac. by Jose Luis Sanchez Brebiesca and Rodolfo de Castello Murisd. by A. L. Swami and A.K.M. Jilanie. by Avittathur Achyuthan and Viswanathan Selhuramanf. Discussions by C. Edward Bowers and Frank Y. Tsai, ASCE Journal ofHydraulics Division, HY1,January 1974g. Closure by Mohammad A. Rahman, ASCE Journal of Hydraulics Division,HY1, November 1974

8. A brief report on repair and maintenance of spillway stilling basinand its ancillary structures, February 22, 1980 thru June 10, 1980,A.K.M. Mukaddas, Plant Engineer, Karnaphuli Hydro Station.9. Bowers, C. Edward and Tsai, Frank Y., "Fluctuating Pressures inSpillway Structures", ASCE Journal of the Hydraulics Divison, HY6,November 1969. (report of some of the experimental data from modeltests of Karnaphuli spillway).10. Movie of hydraulic and structural model tests of Karnaphuli spillwayconducted at St. Anthony Falls Experiment Station, Minnesota, U.S.A. todetermine cause of spillway failure, 1962.

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2. Using the updated IDF, the operation of the spillway and outletsshould be reviewed with regard to reservoir elevations and the downstream effect of releases.3. The dam can be raised fairly easily by excavating part of the damcrest to make a good bond with the existing core, and raising the damtoward the downstream. Such a scheme would minimize any need forlowering of the reservoir.

Gate StructureThe condition of the gate structure concrete was excellent with no signsof distress or movement noted. Th e piers, crest, drainage gallery, andbridge concrete contained only a few hairline cracks (photos 1 and 2).The drainage gallery had about 2 inches of water on the floor (photo 3).No drainage wa s noted from the outflow ends of either the drainage galleyor drain outlets. Water was standing in the 4-inch-diameter cleanoutpipes at each drainage hole to a depth of about 9 inches below the galleryfloor. The readings from piezometers in the piers indicated pressures inthe normal range expected. Survey measurements (vertical and horizontal)indicated no apparent movement of the gate structure had taken place. Anadditional survey was made while we were at the site.

Conclusions1. The structural condition of the gate structure appears excellent.2. The gate structure ha s apparently not experienced any movement orrotation.3. The drain lines from the drainage gallery and drainage holesrequire cleaning as soon as practicable to ensure that they are workingproperly.

ChuteThe walls that could be examined above the tailwater level appeared to bein excellent condition. The to p two floor slabs were above the tailwater. The slab surfaces show some minor areas of weathering and erosion(photo 4). Some small holes are present where pieces of aggregate havebeen plucked out. Some short hair line cracks are scattered over theslabs but they appear to be shrinkage motivated and not structural related.The horizontal "crack" in the top slab appears to be the constructionjoint between the original concrete and th e replacement concrete constructed to repair the 1961 spillway failure (photo 5). The (crack)joint appears, for the most part, very tight except for some areas whereweathering and erosion have increased th e surface width and as a resulthas become more visually apparent (photo 6). The joint had been filledearlier for part of its length but the filler has been mostly eroded ordislodged by flowing water and weathering effects (photo 7). It appearsthat when the chute wa s reconstructed, the concrete was not saw cut and itwas apparently broken to as straight a line as possible using available

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impact tools (photo 8). This resulted in a wavey line appearing tomeander like a crack. The joint does not extend into the walls, andterminates at the longitudinal joints defining the edge of th e wallfoundations on each side of th e spillway.The lower reported horizontal "crack" was under the tailwater at the timeof th e examination.Each chute slab contains a pair of 2-inch pipe drains as is shown on thedrawings for reconstruction of the spillway. These were not a part of theoriginal design. A few of the drains were probed. Some were clear to adepth of 10 feet while others to only 2 feet in depth and presumed to beplugged with silt because the end of the probe brought ou t a silty materialOur examination noted that the downstream side of the contraction jointbetween the gate structure and the chute slab at spillway station 9+44.52was higher than the upstream side inmany bays (photo 9). No evidence ofcavitation related to the joint condition was evident although manyspills have occured.Contraction joints in the chute are filled and sealed annually and theywash out every year (photo 8). Some of the original asphalt impregnatedcork joint filler was still in place. At several locations, the jointcould be probed to a depth of 24 inches. A mortar type filler was alsonoted in some joints. We were told that this material had been usedduring past maintenance work. From photographs of th e spillway failure,itwas obvious that the foundation isvery erodible.It isbelieved that the piezometers beneath and at th e surface of thecenter bay chute slabs, Drawing FL-13-1233R1, were read during earlierspills after the reconstruction (photos 10 and 11). These data should belocated at the project office. We discussed the reasons for the piezometers with project personnel and expect they will read them for futurespills. During the demonstration spill, in our presence, an attempt wasmade to read three of the piezometers. All were dry at about a 62-footlength from the top of the pipes. The spill was not large enough tocreate pressures that could be read in the piezometers.

Conclusions1. The walls and floor of th e chute appear to be performing in asatisfactory manner.2. Small holes and weathered areas in the chute floor slabs requirepatching with epoxy bonded mortar and/or with epoxy bonded concrete.The appendix contains procedures and recommendations for materials.3. The horizontal "crack" which is located 5 feet downstream of thecontraction joint at spillway station 9+44.52 appears to be no morethan the construction joint between th e original concrete and the 1961slab replacement (see Drawings FL-13-1234R1 and FL-13-1235R1).

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4. The lower horizontal "crack", which is located 4 feet up the slabfrom the chute block dentates, should be examined when the stillingbasin is dewatered. It is assumed that this "crack" is the lowerconstruction joint between the 1961 slab replacement concrete and theoriginal concrete.5. The horizontal construction joints (cracks) should be sealed. Inthe appendix are recommended procedures and types of material for thispurpose.6. Review the adequacy of the existing slab as shown on DrawingFL-13-1234R1 and FL-13-1235R1 considering transient pressures, afterdetermining the adequacy of the foundation. Data from the chutepiezometers should be utilized in the review.7. To ensure that there is an adequate foundation, we recommend a coredrilling program be undertaken. This program should consist of aseries of 4-inch-diameter holes drilled through the concrete slab to adepth of 3 feet into the foundation. These cores will indicate thepresent condition of the concrete, foundation, and foundation-concreteinterface. These holes should be drilled in spillway bays 4, 9, and 12at about 4.5 feet right of the slab centerline. The holes should belocated at spillway stations 9+55 +, 9+67 +, 9+86 +, 10+08 +, and10+24 +. If these cores indicate aOn unsatiTfactory-foundatin condition, a redesign and remedial construction may have to be undertaken.However, no evidence of foundation problems were evident in our examination. The core holes should be filled with concrete rodded toensure good density. The surface finish should be as smooth as possible to prevent cavitation.8. The misalinement in the spillway grade at the contraction jointlocated at station 9+44.52 has not shown any cavitation during priorspills. Therefore, we recommend not modifying the joint until cavitation has been noted and then treat the condition locally.9. The contraction joints in the chute slabs need to be filled withfiller material and a sealant. The appendix contains information aboutfiller-sealer combinations and recommendations for materials andprocedures.10. The 2-inch pipe drains in the chute slabs need to be cleaned.

Stilling BasinA large portion of the stilling basin was under water and could no t beexamined. The walls above the tailwater appeared in good condition.Minor local cavition of the basin floor and dentates were repaired in 1980which was the last time the basin has been dewatered. Cavitation andsurface erosion occur in most basins and they need periodic repair.However, a large amount of money can be spent on trying to keep it likenew. Unless the basin has eroded to a condition where a considerableamount of reinforcement is exposed, th e repair should only consist of

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patching deep holes and exposed areas of reinforcement. Repair of localerosion or cavitation damage-in a basin can usually be made by usingepoxy-bonded epoxy mortar or epoxy-bonded concrete. If severe damage hasoccurred, a concrete overlay slab would be required. "Standard Specifications for Repair of Concrete" ha s been included in the appendix.

Conclusions1. Dewatering and examination should be scheduled at periodic intervals such as every three years. Underwater examination by divers couldalso be used.2. When erosion and cavitation damage extends over a large area of theslab, an overlay of reinforced concrete should be considered. Aminimum slab thickness should be 6 to 9 inches. A minimum layer ofNo. 6 reinforcement bars at 12-inch centers, each way, should be placedin the overlay.3. Installation of No. 8 reinforcement anchors should be considered toanchor basin floor to the foundation if an overlay is ever considerednecessary.

Channel Downstream of Stilling BasinFrom our examination of the stilling basin and downstream channel, it wasnoted that many of the cubic-yard-sized concrete riprap have been movedfrom their original position and were deposited in the downstream riverchannel (photos 12 and 13). Many large Oppressions were noted where theriprap had washed out (photo 14).

Conclusions1. The channel protection must be repaired prior to any additionallarge flows to fully protect the downstream end of the concrete basin.2. The crushed-brick concrete blocks are not of adequate size toprotect against most yearly spills.3. A reinforced concrete slab could be placed downstream of the basinbut would require an extensive underdrain system to minimize uplift.If a slab were used, we would recommend using No. 8 reinforcementanchors at 10 foot centers each way grouted approximately 8 feet intothe foundation. Moreover, to ensure adequate strength and erosionresistance, a slab with a thickness of no less than 2 feet should beused.Another alternative to consider would be the casting of new interlocking concrete blocks which could also be anchored to the foundation. Alternatively, the existing riprap blocks could be utilizedagain if they were placed between a series of parallel concrete wallsor lattice work walls to hold them in place. These are all schemeswhich should be considered in a cost comparison study to determine themost feasible option.

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Right Bank Slope StabilityThe right slope of the spillway channel downstream of the spillway cresthas eroded by at least 10 feet since the dam was constructed (photo 15).The residences at the top of the slope will be affected if the erosioncontinues (photo 16). Some cracks now appear on the level area betweenthe top of the slope and the row of buildings. A number of groutedreinforcement type rock bolts are projecting from the slope. The slopeis composed of shale that is continuing to weather and erode by fallingoff along the closely spaced vertical joints through the shale beds(photo 17).

Conclusions1. The slope will continue to deteriorate; however, the process can beslowed by covering the face with a mesh reinforced shotcrete. Rockbolts should be used to fasten the mesh to the shale slope. Drains arerequired to prevent high water pressures from building up behind theshotcrete.2. There should be some consideration given to moving the buildingsfrom above the right slope if the erosion continues.

IMI. MAIN DAMA thorough examination of the main dam found no serious deficiencies. Thestructure is being well maintained and monitoring data"are being meticulouslycollected. The road on the crest of the dam is paved with concrete. Alljoints between the slabs of pavement were well sealed with asphalt, nodifferential displacement was noted between adjacent slabs, and no signs ofdistress such as cracking were noted in the slabs (photo 18).On the downstream slope of the dam is a system of longitudinal and transversesurface runoff collection ditches (photo 19). The ditches are paved withconcrete slabs of 3- by 1-foot size. All of th e ditches were in alinementand grade, and no distress was observed between the paving slabs (photo 20).An excellent stand of grasses covers the entire face. The grass is cut forfodder and used for grazing. Evidence of mole tunnels wa s found in someareas. These animals only disturb th e surface. Very few wet areas werefound on the abutment and these seeped only minor amounts. We were told thatthey practically dry up after the monsoon season.Slope protection on the upstream face was in excellent condition (photo 21).The protection consists of cast concrete cubes of about 1/ 2 cubic yardchinked with cobbles and hard bricks. No signs of erosion, beaching, orsettlement were found and we were told that there has never been wave damageto the slope protection.The instrumentation is well maintained. Periodic readings are taken andmeticulously recorded. We observed the measurement of the piezometric levelfor one of the crest piezometers. The instrumentation data have not beenplotted however, which makes it difficult to fcllow the performance of thedam and identify developing problems. We reviewed the data and discussed

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graphical displays of the data with Mr. Mukaddas, Examples of Bureau graphical displays have been transmitted toIUSAID, Dacca for forwarding to PDB,KaptailConclusions1. The: main dam is in excellent condition with no evidence of detrimentalsettlement or movement.2. Monitoring ha s been'exceptional, however, the data should be displayedgraphically.3. -Continue the present program of maintenance, but increase the programfor clearing woody vegetation'from the abutments for a distance of about25 feet beyond the perimeter drainaqe ditches.4. The relief wells should be inspected to check if cleaning is nowrequired. This should be done periodically. Examination of the flow datamay also iidicate requirements for cleaning.5. An evaluation of the stability and performance of the dam should bemade using the data from all of the instrumentation, surveys and seepagemeasurements.

IV. POWER FEATURESGeneralWe examined the powerplant, intake structure, slope upstream of powerplantand tailrace area.P.werpl antThe powerplant wa s well managed and maintained. The people working in thepowerplant appeared to be very dedicated to th e project and take muchpride in their work. The third unit wa s being installed by the VinnellCorporation and the work was reported to be progressing satisfactorily.Mr . Jim Hill, Vinnell Corporation, indicated that the unit appeared tomeet or surpass all required tolerances and should operate with minimalvibrations. He indicated that the vibrations from the unit should be nogreater than those of the other units.

Conclusions1. The concrete in the substructure and operating deck appeared inexcellent condition and nearly crack free,2. No areas of movement Or. distress Were noted.3-' The structural steel superstructure appeared to-be in excellentand wellmaintained.1condition

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Intake StructureThe concrete in th e intake structure was in excellent condition. No areasof cracking or other signs of distress were noted. The metalwork andequipment were in satisfactory condition and repair, except that some arein need of painting. Continual maintenance isrequired to maintain goodoperation. No problems with the operation of equipment were reported. Weexamined the forebay area and discussed the possibility of increasing thestructure size for two more units.

ConclusionsThe intake structure is in good condition and should continue tooperate properly if well maintained.

Tailrace Channel SlopesThe left tailrace slope was originally supported with grouted anchor barsand face plates. The left bank slopes from the channel bottom to a bermat the approximate elevation of the top of the retaining wall immediatelydownstream of the plant retaining wall (photo 22). It is then vertical tothe to p of the cut which is at approximately the elevation of the powerplant entrance. The berm appears to coincide approximately with a changein the angle of the joints cutting the horizontally bedded rock. Belowthe berm, the joints are at a small angle from the vertical, sloping intothe channel; while above they ar e vertical. The rock has slipped out frombehind the face plates for about a distance of 5 feet at the level of theberm.The right tailrace slope geologic structure is the same as the left exceptthat the top of the slope is about 50 feet higher and a fault cuts throughthe slope at the end of the right retaining wall (photo 23). Some smallareas of vertical slabs of the approximately horizontally bedded rock havefallen into the channel. A large block of rock above the fault has alsorecently dropped into the channel. The block was defined by the fault,vertical joint set and down dipping of the bedding planes due to thefault shear. Downstream of the fault area, the right slope is almostvertical. Rock falls from the slope in vertical slabs of 6- to 12-inchthickness. Weathering of the almost vertical joint system governs thewidth and thickness of the slabs (photo 24). Several temporary structuresand a tower carrying lines to the switchyard are at the to p of the slope.The tower is presently about 50 feet from the edge and could be movedabout 40 feet further away from the slope. Operation of the third unitmight cause increased rockfall until a more stable configuration is againachieved. Water was standing over a large area at the to p of the slopenear the tower.

Conclusions1. The tailrace channel slopes will continue to experience ravellingbut this is not of large concern.2. Surface drainage from the top of the slopes should be improved andmaintained to minimize infiltration.

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3. At some future time, moving the tower may be desirable when sloperavelling has come closer to the tower.4. With the third unit in operation, if scour of the base of the rightside of the channel becomes a problem, a masonry wall could be constructed underwater by stacking large blocks of concrete. The spacebetween the wall and slope would be filled with free-draining material.A cast concrete wall would be considerably more expensive.5. Installation of horizontal drains into the mass above the faultplane and through the fault would enhance the stability of the area byrelieving the excess pressures.

Slope Upstream of PowerplantThe slope upstream of the powerplant was excavated in four rises. Thefirst rise from the powerplant entrance level was vertical to the firstberm. Then the other rises had a slight slope to the remaining two bermsand top of the excavation (photo 25). During construction there wasapparently a stability problem with the slope in back of the left end ofthe powerplant requiring additional excavation and redesign. Here thereis only one berm at about the level of the second berm on the right side.A concrete retaining wall was constructed on the berm and retains a slopeof stacked handplaced rock which is capped at th e top by a concrete slab(photos 26 and 27). Mostly grass-type vegetation grows on the naturalslopes and berms, but some trees are starting to grow (photos 25 and 26).Weathering and erosion of the first rise cause a continual cleanup problemduring the rainy season (photo 28). Erosion has progressed in somelocations to where there is only one slope to the second berm. Measurescan be taken to slow the weathering process, but periodic reconstructionof protection will be necessary to minimize slope erosion

Conclusions1. Treatment of the lower shale slope can reduce th e erosion andcleanup problems. The slope should be cleaned back to sound shale.Short anchor bolts with wire mesh and shotcrete applied will reduce theerosion. Weep holes need to be provided through th e shotcrete toprevent buildup of water pressure.2. Infiltration of surface drainage should be minimized. This may beaccomplished by stripping each berm of vegetation and paving thesurface and ditch at th e back of the berm. Slope the paving to draininto the ditch.3. All vegetation other than grasses should be kept from growing on ornear the slope.

Drainage GalleryWe examined the access tunnel and the drainage gallery in the hill upstreamof the powerplant. Both th e tunnel and gallery are in shale. Verticaldrains pierce the roof of th e gallery (photo 30). The drains ar e gravel

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packed, 4-inch PVC or steel slotted pipes. The tunnel and gallery wallsfor the most part are in excellent condition (photo 31). The gallery tothe north of th e access tunnel has fewer supports than to the south.There were more spalls and small rock falls inthe south gallery (photo32). There were no large areas of spalls noted. About 16 gal/min wereflowing from the tunnel. Mineral encrustation of the drains was visiblefrom the gallery and ranged from minor to severe (photo 33). The electriclighting system in th e tunnel and gallery was out of order.

Conclusions1. The tunnel and gallery are in generally excellent condition. Bothshould, however, be surveyed to locate areas of potential rockfall.Loose material should be removed and the surface shotcreted or additionally supported in problem areas.2. All the vertical drains should be cleaned. Design drawings showthe drains to exit through the top of the hill. Examination of thedrains from in the gallery also indicated that they were originallydrilled from the ground surface. If the tops can be located, cleaningwould be facilitated.

Access Road SlopeThe portion of the access road of concern is along the curve immediatelybefore th e powerplant entrance gate. The road lane closest to the slopedown to the river has an arcing crack pattern which is about 50 feet longand extends about 9 feet into the lane (photo 29). The cracks have beensealed with asphalt. There is only a very small offset at the crack. Noevidence of vertical displacement could be detected in the grassed areabetween the road and th e slope. The slope to the river is steep, andsloughing could be seen from the edge of the slope. The undergrowth,however, was too dense to make a detailed examination of the slope.

Conclusions1. Instability of the slope mass, with a very small slope movement,could be responsible for the arcing crack pattern in th e pavement. Theinstability could be seasonal and dependant on water infiltration.2. Horizontal drains installed into the hillside below the road wouldenhance the stability of the slope. The drains should penetrate thehill to a location approximately-beneath th e drainage ditch along theeast side of the road.3. Survey monuments should be placed in the crack area and in thesurrounding pavement to monitor changes in elevation and movementtoward the river.4. Design of any additional remedial construction will depend upon thecharacteristics of a potential slide, i.e., does the potential slideencompass the full distance to th e river or exit up on the slope? Is

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the slide insoil or rock? Relocation of the access road further intothe hillside may prove to be the simplest solution.

V. CARGO TRANSFER SYSTEMThe primary examination of the cargo transfer system included the slope abovethe river, the top of the slope, and the tower footings. The second tower upfrom the river (photo 34) had foundation rock exposed beneath the left sideof the footing when looking up the slope (photo 35). Temporary measures havebeen employed to attempt to hold the soil. Exposure of the soft rock willhasten weathering and erosion, and eventual loss of support for the towerfooting. Examination of the concrete members of all the towers revealed nodistress whatever. All appeared structurally sound and without differentialmovement. No cracking of the concrete was evident where th e steel structureattached to the concrete. The steel superstructure needs cleaning andpainting. There are surface drainage ditches to carry flow away from thefootings, but they need cleaning. Uncontrolled surface runoff was alsoapparent (photo 36). Woody growth had established itself on the slope. Suchgrowth will aid the break up and deterioration of foundation rock on theslope.We were additionally asked to examine the monorail beam. At some locations aplate which was welded under the lower flange has horizontally separated fromthe monorail beam. Grease and sheared metal did not allow a close examination. We were told that the system ha s many breakdowns and delays. It wasdown during our examination due to repairs of the hoisting mechanism.

Conclusions

1. The concrete towers and footings are in excellent condition with nosigns of distress.2. The foundation for th e second tower footing should be protected todecrease deterioration of the soft rock. This can be accomplished byconstructing a cribbing system to hold protective soil against the hillside rock. Before covering the exposed foundation rock with soil, itshould be cleaned to a sound surface and a protective coating such asshotcrete applied.3. Surface drainage features must be maintained and improved where thereis concentrated runoff eroding the slope.4. Woody vegetation must be kept from growing an y where near the towerfootings.5. The monorail beam should be cleaned and examined by a structuralengineer. Fabrication drawings should be reviewed and an evaluation madeof the capability of the monorial to support the trolley.6. Inspect steel superstructure for signs of member and connectiondistress.

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VI. OUTLET WORKSGeneralThe upstream tunnel and intake could not be examined because they wereunder the water. We examined the downstream end of the tunnel by the useof a sampan. The tunnel could be examined with only th e light from thedownstream portal. We entered the gate shaft from the control buildingnear the right abutment of the dam.Control Building and Access ShaftThe building contained a reservoir level gauge and the operating controlsfor the outlet gate. The equipment appeared, in general, to be in satisfactory condition. We climbed down a spiral staircase to examine the gatebonnet. The shaft was dark because many of th e light bulbs had beenremoved. The low level outlet works is an important feature used forreservoir evacuation in an emergency to ensure dam safety. Without properlighting, it was difficult to fully examine th e gate bonnet and otherequipment. However, it appeared that th e shaft and equipment should becleaned and maintained. The missing ventilation fan should be repairedan d replaced as soon as practicable.Downstream Diversion TunnelThe concrete in the tunnel appeared in good condition. Some rock pocketsand voids could be seen in th e walls downstream of the portal. Thesevoids, although unsightly, will not affect the adequate operation of thestructure. The downstream walls and tunnel lining contained very fewsmall cracks and the structure showed no areas of distress.

Conclusions1. The outlet works and diversion tunnel appeared to be in satisfactory condition.2. The liqht bulbs and ventilation fan need to be replaced ,3. The shaft and equipment need to be constantly cleaned and maintained

141


21/59

APPENDIX


22/59

BANGLADESH POWER DEVELOPMENT BOARDOFFICE OF THE MANAGER (POWER)

KARNAPHULI HYDRO STATIONP..O 'KaptaiCTG. Hill.Tracts

NO:M-10/81/4031(12)MINUTES OF THE MEETING HELD ON SEPTEMBER 22, 1981

Ameeting was held on September 22, 1981 at 4:00 p.m.at Biddyut Bhaban -. Thefollowing gentlemen attended the meeting:PDB

1. Mr.*A.F.M. Moeenul Islam, Manager, KHS2. Mr. A.K.M. Mukaddas, Dy. Manager, Plant Engineer, KHSBureau of Reclamation, U.S.A.

1. Mr. Richard W.Kramer, P.E., Asst. Chief, Dams.Branch Division,2. 'Mr. Rolph Atkinson, Head, Concrete Dams.and Spillway,USAID

1. Mr. Shamim.Rahman, General EngineerThe .following discussions were held and decision taken:

1. All the problems of civil nature faced by Karnaphuli Hydro Stationshould be investigated per the following program and advice providedaccordinqly.2. Scheduled the following program of work during the stay of theBureau of Reclamation team:

22-9-81 - Visit of spillway, powerhouse and other places to have aMorning general idea about the work involved (already done).Afternoon - Study of drawings, photographs, and discussion on'connected4:00 p.m. matters23-9-81 - Inspection of spillway chute and the crack by going on theMorning spot from downstream, inspection of riprap, erosion at the8:00 a.m. tailrace, etc.

- Inspection of spillway drainage galleryAfternoon - Inspection of Main DamEvening - Study/survey;data of spillway and piezometer,.readings,

etc._instrumentation 'data of the*dam,


23/59

24-9-81 - Inspection of Cargo Transfer System and the erosionMorning at that place

- Drainage gallery in the hill behind.the powerhouseAfternoon Inspection of hillside behind powerhouse

- Inspection of erosion attailrace of powerhouse- Inspection of erosion beside' approach road to powerhouse

25-9-81 - Inspection of diversion tunnel gate shaft and downstreamMorning side- Operate spillway and study'restriction in operation ofthe same

Afternoon - Discussion and study of drawings and reports26-9-81 - Discussion on the inspection.,doneMorning12:00 - Departure for Dacca(Noon)

A.F.M. Moeenul IslamManager (Power), K.H.S.

cc: 1) The Member (G&T), PDB, Dacca2) Th e Addl. Chief Engineer, (G&T).3) The Chief Engineer, USAID, Dacca4) Th e Plant Engineer, K.H.S.5) Mr. Rolph Atkinson, Head, Concrete Dams and Spillway and Outlets Section6) Mr. Richard W. Kramer, P.E., Asst. Chief, Dams Branch - Division of Design

2


24/59

Photo 1. Spillway gate structure access bridge,

Photo 2. Spilway gate structure drainage gallery.


25/59

jj

Photo 3. - Water standing in spillway gate structuredrainage gallery.

I

Photo 4. Spillway chute slab surface showinq sliqhterosion and the "horizontal crack."


26/59

w6

Photo 5. Horizontal "crack," joint between originalconcrete and 1961 reconstruction, runs upcenter of photo. Contraction joint betweengate structure and chute slab at spillwaystation 9+44.52 is to the right, up thechute.

"...:". ,: ? -' * '-V-J.k,,

. ".'- ; Z , , ' - '01 "

f

. .I ... '

'

...

Photo 6. Construction joint between original spillwaychute slab concrete and 1961 slab replacement.


27/59

, -i,,, , : ,.,, . o.+..'.ky

It.- It 'ki... .., . ,. , . .,O

Pk 07; 0+1At.'t Photo 7. Horizontal construction joint (crack) with some

p)ortions still havinq filler in place. Thisis the only offset inthe crack and appearsto be the origi nal shape.

'":" ":,("i,"",,&r"

Photo 8. Horizontal construction joint at one of thelonitudinal contraction joints. Note thataggregate is not broken across joint and the.......lower (left) slab concrete was placed over

the upper slab at the joint where the concretewas broken away.


28/59

,. +'flHrr." ~**~

I 41

Photo 9. Contraction joint between gate structureand chute slab.

i """ . ... " ' , " ","""'"++.....

,+ + ',. - ,,". ,i+ ++* j . ,r - .

. .. . .. ..... . .. . ..'1 I1114~>

8J'* . L ' . -" e; P +. ., -,

I a% 1.T 14,*.7 w, ~

Photo 10. Piezometer in surface of chute slab.


29/59

Photo 11. - Piezometer pipes extending up centerbay pier to reading station.

Photo 1?. - Channel downstream of spillway stillinobasin showing the riprap blocks whichhave been washed from immediately belowthe stillinq basin.


30/59

4,

44.

Photo 13. - Cubic-yard concrete riprap blocks asplaced. These are along the leftbank below the stilling basin.

Photo 14. Sandstone along left side slope ofspillway outlet channel. flown-stream of the stilling basin,large depressions have been erodedinto similar bedrock.


31/59

Phot ,o... s,t .chute and illn b N

,~ nco ; ' 10 . to.,;ars. prtudn 12 feetPhoto 16. Right spillway adjacent to h/ ''p

Photo 15.- Right soo spiliwaye adjacent toche

a s

and stilling basin.


32/59

_.,~~J0,' ' '.V ,, ' "I

Photo 17. - Right spillway slope showing nature ofexfoliation of material.

., .. : .

Photo 18. - Road pavement on dam crest looking towardleft abutment.


33/59

.. -- - "---

Photo 19. - [ownstream face of dam with surfacedrainage ditches.

Pot.o+ 20. Drainageditches.9' 4' 'o+ , ,.

-Dritaghto20 itches.++


34/59

Photo 21 . - Slope protection on upstream face.Growth at waterline is waterhyacinths. They are a continualmaintenance problem.

Photo 22. -Left tailrace slooe. Note anchorswith face plates on slope belowbe rm.


35/59

Photo 23. - Right tailrace slope. Note fault andhole where block dropped out intothe tailrace. Lower right side ofphoto is at about end of plantretaining wall.

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* _o ' A1 . *- 4(.

4410

Photo 24. - Right tailrace slope downstream of thefault.


36/59

Photo 25. - Upli)per Iwo berms on s11O)(. up s treamof the right side of powerplant.

ti~ V

Photo 26. - Slope upstream of the left side ofpowerplant with hand-pl aced rockabove retaining wall.


37/59

Photo 27. - Concrete cap on top of slope upstreamof the left side of power!)lant.Note surface drainage at top ofexcavation.

Photo 28. First rise in sIope ups t ream of thepowerplant. Note progress of erosionat far end of slope and cleanup inprogress.


38/59

Photo 29. Cracking in powerplant access road.

Photo 30. - Vertical drain pielrcing roof of drainagegallery in hillside upstream of thepowerplant.


39/59

Photo 31 . - Drainage gal lery upstream of powerplant. Shale is generally inexcellent condition.

Photo 32 . - Minor rock falls in south end ofdrainage gallery.


40/59

Photo 33. - Mineral encrustation of lower, portionof vertical drains.

Photo 34. - Cargo tra nsfer system tower fontinqs.Second tower is in the foreground.Boats are waiting to be lifted toreservoir.


41/59

r'Ie"A" . ,'.L . _,

Photo 35. - Footing for s,,eon! Lower. Foundationexposure is at. left side. !'Notetemporary retaining scheme to holdsoil oil slope.

Pr

Photo 36. -Soil erosion and builIdup of wqoody growth.


42/59

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olorvinforvernens &rill-- conzrol.W th

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43/59

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44/59

P/EZOME TER? EEVATION.Piezoimt/er number fetvc,/,c.

-5 1 A--44.24.9S2- 40.2,09JJA-- - --- --A 44A- -- 3. ,jiA J5A- * 24S24%36A -* 19.143%T8A- C/338. 326C

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Ip~,o~ oul/etz 3ha// be meisjar,d and recardled. wl- ~*C~46/2.rHeads Wfall pezarne/er rua7 .sial',4vlhor j /mped an

yru h) ir/~,oo i wvi/h piezolia&-.nuimbr a ws,ivmj on 1e p/in.4 41

REFERE'NCE DRAWIS.kpa/vay chule ae ld4A*//.V b~s, .slats Re,,force. ahed-cKp07U1101. fLf VAT/ON F-F Jp la rpi i/c l/ie /a- Rsn6rameent -- 1-3-12.9

4-4 4**- 4't4' ~ iEb ed'~PIA ?4 A DO:GOVERNMENT OF PAKISTANI MINISTRY OF INDUSTRIES

4 r- JA~ KARNAFULI PROJECT.-M A L J1,

d;' drIsdwilh SeC7YON' c-c CH'L'Tf AND $?A4NbGa. holes.ffo/lofrp~.e' -______ PRESSVRE P/fZONT1E[RS.

j-f INTIENATIONAL ENGINEEfRING CO.. INC - ENGINEERSDf*rO!. ? CMKa--V. .-.- 4-M4

I 0I ~ MA...uCOuNDriot71.92 hAAMeA DRAWNI As built j APmv-a11ICD- ATXSo -1"0 196/ L "
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45/59

I

7'K-3C ~Porowre~rif o,'ui,rozqh allernuk ontamjv~s.91tWhd3

Ac orweld7eiv 'IV

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TY~iCAL PLA

Sleell

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46/59

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TYPICAL PLANCHUTE &LABS-LEFTABUTAIENT

.9f4.5R2-JiRequlred

*- .% drcex-v.8. &wn . ..ofd, . -a., 3'e,,,pen-enI..

CO,7COfb*Js ......47t" "**.,. '.. , " '- a po'ous_ "- l n ..,. ...a.,.-.-. -,

?A, 6 cover slabs.

recPecou porous 14/" "..." ,g d KFLeh3,-nOn..( I.m".,,f_ u s o,,.."L 0.lX-,.~ . - C_q.-. A>-. *.*,y." ,,T...ocretedree/ppe.... . i .*t

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47/59

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2,/./0 t?,27KEY PLAN

"".' , ,.NO M5 :Feather r"gv are/to1 voMkJ in olowhny k cocrete &l.

Al l con4./r4Tetioljoo/.I isdn lean concrels f171/I/ hel/'e r/g, M o11"cleaned and Irealed oa tnrnV cons/ru:lionjint%.sab3. 6 over Poroe concrete draaniunder Iab6 ttr-*jh h'lln,/denta/es 3h/lbi a'rraigod to as 3 riswiII/3/:lahi 8/Saubk

' ' RFEcRENCE DRA WIN& T/- " -Spi,/ay ra/nole parrC ple l,;"fl/A chute and f ....4Weepollway repairs to chw/c I*pca/ dal''/ - -d35V. yllw boaso /.s'6b rem forcemenlhut/ and jtfifng6Precastporous -&-J0

infmaes mw 2!eiiA sa hoclbdwg KF/3"404 pour under dam e ns/rjt

Por m ollhnoAc,h ao.(Comira/ . /CTION B-BCHUTE SLAB8 % &2 .V . FROM LErA ND rAIep 0F3 as c/e LEFT' PORT/ONGOVERNMENT OF PAKISTAN* concrete MINISTRY OF INDUSTRIESxjyKARNAFULI PROJECT%SRLLWAYREA RS 7V CMaTE IOUT/,N-REINFORCZMENTI

_ II_ _ INTENATIONAL ENGINEING CO. IMC. - INGINEEIC 'L.42 1/w I

U.I w XNFTALSA~l PAIWAAN-SI ICA.X-1 nL/92JRJ -tv


48/59

No1'. AlfanfuemantJet d. P -13

bey rein orcemeW6donm~lc, see dsY. Mf-,3; 2 L, 2" " .fvert I..00 ,,

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TYPICAL DETAIL < I3/7ow//y por-ou Conct!'ee aI~h/drain ouI/el pipes.So/abs 8.9.1011.12./3 (/4 fr k/-1) sleel pipe Sid

p./0,#.O+9.S? F.-,,O4.,weldotet, ' o

..-Con sIJ/ .. 3.O0,, _ _ _.. " , .

* ~1~ /P'ff/JV~ ~ ~ C.Lh6 nv, gradrad 3WrV

TW/."AL DETAIL TYPICAl.. DFTAIIflr broken .slling basin droinae p#pex for St/lhin basin drahage pipes pulledprojecting beyond Ihe basin slabs out of the bohin s/a6s

-Coer - ood.3'kJ/ , a i t replace as Ai4 fn 8gi12awe , 0'6 bar

had-ShaleSIAM" -~" I',,,- .. . . . ..DETA /I POROUS CONCRETFSea/ s/oh 6c l/jo n[ " Iof slabs on Sa1d,1 DtT,IL AT LI6HTL Y DRA/N IN SHALEDEpRqS$D DEN/TA ;-f /'O*CALf. Z

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49/59

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rZ~ ~ 4'~/d~saaippa 2

TYP/CA.ETAIL- CA755 A/u*~,oaa~ata Pehe ~ow~ n WE /

dhere slabs roul/els.

T~~ ~ ~~~lIA DETCA''DILA bw l 5/1-Jan da/1/ /,?' poyaa

a/ damaged/pells sp~wh Mr;oi9 denlets.

KSPSFR~ JA/N drrdie;*d 0fcL Inyranae ~ppe ~basn ~lk o

-. ,Ox Cocret

Awn'-, 5oco&urak in~olp Weetcin Io,~

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50/59

19-8!,6e50 dowels 21-,,thero . WA mw. between dinathsand two obuot *a/afle' W'I//dnd'9,ou'e'l offe, ?4 OJ2gyxta (P5dse pie heirdirnIv-~ Cuts~bh I

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~~~en1mor renfrr'al areainas~bh,,bcliCif.L lJvrff,winyinorie0/exst? DU')e;M

to lbfo,cho'n~~~~Zterot isiiml 3d olSdTS:610Y r~lchutef4Jlaedhwh

&Sj/ 'ffperfordtiorn of reilet w&// ^DesIf,:ara d.nfai oA 6.lfobie dioAf. or

fd 9cs of biroen sakhs 4o to 7a sha/hbe17 Manedl ajsdirected after .suppodi.'9G,,nd~~~ae Maicefusn cofleft/e i placfd.

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.Vo1l0-49.52

1ChipbaW spolid concreteC/soAan rd rep/ac, vithorOf GOVERNMENT OF PAKISTAN

- .. *-.* 7~MINISTRY OF INDUSTRIES:zL ~,,,$ XL -- KARNAFULI PROJECT

4 RtPAIe TO C//UYT!I TYPICA L .DE 7A /1-S

TYPICAL DETAILof tit ofewitinM, den'sWei INTERNATIONAL ENGINEUIING CO.,INC. - ENGINEERS

I f,to new Concrete.slabs 4,5.~4andl5frem

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W o~ra M' :26. /S I


51/59

TECHNICAL SPECIFICATIONS AND'STANDARDS

(1) Standard Specifications for Repair of Concrete (M47), Bureau of Reclamation, Denver, Colorado, April 1981(2) Standard Specification for Epoxy-Resin-Base Bonding Systems for.Concrete,ANSI/ASTM C 881-78 American Society for Testing and Materials,

Philadelphia, Pennsylvania, 1978(3) Standard Test Method for Bond Strength of Epoxy-Resin Systems Usedwith Concrete, ANSI/ASTM C 882-78, American Society for Testing andMaterials, Philadelphia, Pennsylvania, 1978(4) Standard Test Method for Effective Shrinkage of Epoxy-Resin Systems Usedwith Concrete, ANSI/ASTM C 883-80 American Society for Testing and

.Materials, Philadelphia, Pennsylvania, 1980These standards and specifications have not been included in this copy of the,report. They ar e listed for informational purposes only.


52/59

KARNAPHULI HYDRO STATI'ONCIVIL WORKSSCOPEOF WORK

1. Spillway"a. Accomplish core drilling program on chute slabsb. Review the adequacy of th e replacement slab, as shown on DrawingFL-13-1234R1 and FL-13-1235R1c. Conduct hydrologic study to review Inflow Design Floodd. Review operation of spillway, using updated IDF, for reservoir.elevations and effect downstream of releasese. Clean drain lines from drainage-holes and drainage galleryf* Repair small"holes and erosion pockets on spillway slabsg.. Seal horizontal construction joints in'spillway chute slabsh. Seal contraction jointsin chute.and stilling basinslabsi. Repair.floor'of stilling basin if requiredj. Design and construct channel protection downstream of stilling basink. Design-and. construct slope protection on right-downstream side of

spillway..1. Develop schedule for dewatering and examining basin',

2. 'Powerhousea. Cleanlower slope in back of-powerhouse and'installwire mesh shotcrete"and weepsb. Pave berms and ditches in back of powerhousec. Desiqn horizontal drains for drainina massabove fault plane at right,tailrace channeld, Improve surface drainage from.,top :of right tailrace slopee. Remove all woody vegetation from slopes andabove slopes around the. powerhousef. Design revetment along base of right.tailrace channel for implementa.tion when necessaryg. Design horizontal drains for draining back of potential'slide.massbeneath access road


53/59

h. Install bench marks at access road slide to monitor for movementi. Investigate nature of slide below access road and design remedialtreatment (most practicable solution maybe that the road shouldbe moved ifmovements become untolerable)

3. Main Dama. Inspect and clean relief wells as necessaryb. Evaluate performance of damc. Clear woody vegetation back from toe of dam

4. Cargo Transfer System-a.-Apply protection to exposed footing foundation and design structure(cribbing) to maintain a protective soil cover on foundationb. Clean and improve surface drainage on slopec. Remove woody vegetation from slope near systemd. Peview fabrication drawings for monorail; closely examine the monorail, especially the areas of purported failure of monorailcomponents, and design remedial worke. Inspect superstructure for signs of member and connection distress

5. Outlet Worksa. Improve housekeeping inaccess shaft, and clean and paint gatesurfaces as required


54/59

OFWIOIAf. oot"O. 1oJULV 1373 (01GSA FpIpi 141 CF"U 10-4I.6UNITED STATES GOVERNMENTMemorandum

TOMemorandum: Head, Concrete Dams, Spillways, and* O

Works SectionDenver, Coloradoutlet DATE; October 22, 1981

FROm : Head, Concrete Section

SUBJECr: Civil Works Repair - Karnaphuli HydroStation, Karnaphuli Third Unit, KaptaiThis memo is in response to your recent request for assistance in selectingmethods to seal construction and contraction joints in th e spillway chute.Specifically, This addresses two types of joints which ar e to be sealed:

A. Construction joints where the chute was previously replacedbecause of failure due to erosion of underlying earthen materials -These joints are somewhat irregular in alinement, probably due tothe original method of excavation. Moreover, these cracks are quitesmall (about 1/16 inch on the average).B. Contraction joints purposely placed in the massive chute floor-These joints are approximately 1 inch wide and very deep (to the limitof visibility in the darkness of the crack).

The following recommended procedures are based on our evaluation and diScussions with you an d representatives of the Materials Science Section.A. Construction joint cracksThere are two recommended methods for sealing the cracks at the construction joints:

1. The first method consists of removing a 24-inch-wide, 3-inch-deeptransverse strip of 'concrete from the area at the construction joint,sealing the crack with a flexible sealer, laying a thin sheet material6 inches wide over the crack, filling the excavated strip with epoxybonded concrete, an d cutting a 2-1/2-inch-deep saw-blade-width jointih the center of the hardened replacement concrete (fig. 1).2. The second method consists merely of sealing the crack at theexisting surface with a flexible sealant (fig. 2).

jThe first alternative method would be a more durable and reliable methodof sealing the onstruction joints. The second alternative method wouldbe much simpler, less time consuming, and less expensive. The durationof acceptable performance of th e second alternative method would dependon many factors including care in application, extent of crack movement,amount of exposure to th e sun, and the extent of abrasion from th e flow,therefore, making it inappropriate for us to predict a service life beyondseveral years.

Be U.S. Savings Bendi, Rlegwlad on th e Payroll Sauiu, PlA=


55/59

B. Contraction joint cracksContraction joints should be sealed by pushing a flexible foam-type rodinto the crack to provide a backing and applying a flexible sealant 3/4to 1-inch thick, with a recess depth (from concrete surface to exposed,surface of the sealant material) of about 1 inch (fig. 3).

1. Materialsa. Flexible sealer should be an amine-cure silicone rubber similarto Dow 790 or G. E. Silpruf.*b. Flexible rod should be similar to polyethylene foam ro d (squareor round) and should be of th e size to fit snugly into th e contraction joint. It should be firm enough to provide a tight backing;for th e flexible sealer, yet flexible enough to easily compress toless than half its original in-place thickness.

c. The thin sheet material for use in repairing constructionjoints may be any inert material which is strong enough to beglued to th e excavated concrete surface and withstand subsequentplacement of concrete over it. It should be flexible enough toconform to larger surface irregularities, yet stiff enough to resistconformance to minor surface features, thus providing a slip surfacefor subsequent crack movement.d. Epoxy for bonding fresh concrete to hardened concrete shouldmeet th e requirements of ASTM Specification C 881 (copy enclosed)for a Type II system.e. Replacement concrete should contain a maximum size aggregatebetween 3/8-and 3/4-inch. Its water-cement ratio should be lessthan 0.45, and the percent sand should not exceed 60 percent byvolume of total aggregate.

2. Proceduresa. The 24-inch-wide strip of concrete to be excavated at theconstruction joint should be removed by saw cutting th e edges andchipping ou t concrete in between. The saw cuts should be 8 to 16inches from th e actual construction joint, and 1-1/2 to 2 inchesindepth. The saw cuts should be as straight as possible, giventh e actual location of the construction joint, and at an inwardbevel (about 150) to ke y th e replacement section into the excavation. Concrete should be chipped out to a depth of 2-3/4 to 4inches. The center 8 inches of the excavation should be as flatas practical.b. Each construction joint to be sealed with flexible sealant,including both th e surface crack and the excavated crack (figs. 1and, 2), shall be prepared by routing out a triangular or rectangularshape section at the crack. This section may have a width of 1/4to 3/8 inch and a depth of at least 1/4 inch bu t not greater thanthe width. A width up to 1 inch may be used if the edges of thecrack are spalled. Special tools are available for routing outth e concrete at th e crack.**

2


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-c., The contraction joint cracks must be thoroughly cleaned to adepth of at least 2 inches. Cleaning shall consist of removingall foreign material and stripping the surfaces at the side ofthe cracks of all coatings, leaving a bare, clean concrete surface.We expect sandblasting with a small nozzle to be necessary.d. The flexible type rod should be pushed into tile contractionjoints to a depth of 1-3/4 to 2 inches from the surface. Ifnecessary,the crack should be cleaned again to remove foreign material.e. The flexible sealant should be applied only to dry, clean concrete surfaces. Itshould be tooled into the concrete surfaces tofacilitate bond to the concrete. It should be finished to a slightlyconcave surface 1 inch + 1/8 inch below the concrete at contractionjoints and should be finished flush with the concrete at the construction joints. It should be allowed to cure for 48 hours before exposureto moisture.f. After the flexible sealant is applied inthe construction jointcrack inthe excavated section (fig. 1)and allowed to cure for 48hours, the thin sheet material should be centered inthe excavationand lightly glued inplace to secure itfor subsequent repair procedures.g. At the construction joints (alternate 1) epoxy bonded concreteshould be placed and cured as specified inthe Standard for Repairof Concrete (copy enclosed). Epoxy bond coat should not be appliedto the underlying thin sheet material.n. At the construction joints (alternate 1)a saw cut expansion jointshould be cut midway inthe hardened replacement concrete to a depthof 2-1/2 to 3 inches.

Sncl'osures,opy to: D-1511D-152C Wr~ '"* See iattached page for alternative materlials.** See attached page'- for a: recommended. router.


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Attached Page

*The material recommended in the memorandum ismost resistant to weathering;however, ifmaterial is to be under water, one of the following (urethane)materials is recommended:1. "Sikaflex 1A," Sika Chemical Corp.2. "Vulchem 203," NAMECO International3. "Sonolastic NP-I," Sonneborn - Contech

**One satisfactory router ismodel JA-I produced by the Windsor MachineryCorporation.


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