ACI 210R-1993 Erosion of Concrete in Hydraulic Structures《水力结构中的混凝土侵蚀》.pdf

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1、ACI 210R-93(Reapproved 2008)Erosion of Concrete in Hydraulic StructuresReported by ACI Committe e 210James R. GrahamChairmanPatrick J. CreeganWallis S. HamiltonJohn G. Hendrickson, Jr.Richard A. KadenJames E. McDonaldGlen E. NobleErnest K. SchraderCommittee 210 recognizes with thanks the contributio

2、ns of Jeanette M. Ballentine, J. Floyd Best, Gary R. Mass, William D. McEw en, Myron B. Pe trows ky,Melton J. Stegall, and Stephen B. Tatro.Members of ACI Committee 210 voting on the revisions:Stephen B. TatroChairmanPatrick J. Creegan Angel E. HerreraJames R. Graham Richard A. KadenJames E. McDonal

3、dErnest K. SchraderThis report outlines the causes, control, maintenance, and repair of erosion Chapter 2-Erosion by cavitation, pg. 210R-2in hydraulic structures. Such erosion occurs from three major causes: cavi-2.1-Mechanism of cavitationration, abrasion, and chemical attack. Design parameters, m

4、aterials selec-tion and quality,environmental factors, and other issues affecting the per-2.2-Cavitation indexformance of concrete are discussed.2.3-Cavitation damageEvidence exists to suggest that given the operating characteristics andconditions to which a hydraulic structure will be subjected, it

5、 can be de-signed to mitigate future erosion of the concrete. However,operationalChapter 3-Erosion by abrasion, pg. 210R-53.1-Generalfactors change or are not clearly known and hence erosion of concrete sur-faces occurs and repairs must follow. This report briefly treats the subjectof concrete erosi

6、on and repair and provides numerous references to de-tailed treatment of the subject.3.2-Stilling basin damage3.3-Navigation lock damage3.4-Tunnel lining damageKeywords: abrasion; abrasion resistance; aeration; cavitation; chemical attackconcrete dams; concrete pipes; corrosion; corrosion resistance

7、; deterioration;Chapter 4- Eros ion by chemical attack,erosion; grinding (material removal): high-strength concretes; hydraulic struc-4.1-Sources of chemical attacktures; maintenance; penstocks; pipe linings; pipes (tubes); pitting polymerconcrete; renovating; repairs; spillways; tolerances (mechani

8、cs); wear.4.2-Erosion by mineral-free water4.3-Erosion by miscellaneous causesCONTENTSPART 1-CAUSES OF EROSIONChapter 1-Introduction, pg. 210R-2ACI Committee Reports, Guides, Standard Practices, andCommentaries are intended for guidance in designing, plan-ning, executing, or inspecting construction

9、and in preparingspecifications. References to these documents shall not bemade in the Project Documents. If items found in thesedocuments are desired to be a part of the Project Docu-ments, they should be phrased in mandatory language andincorporated into the Project Documents.pg. 21 0R-7PART 2-CONT

10、ROL OF EROSIONChapter 5-Control of cavitation erosion, pg . 210R-85.1-Hydraulic design principles5.2-Cavitation indexes for damage and constructiontolerances5. 3- Usi ng aeration to control damageACI 210 R-93 s uper s e des ACI 210 R-87 and became effective September 1,1993.Minor revisions have been

11、 made to the report. Year designations have beenremoved from recommended references to make the current edition the re-ferenced version.Copyright Q 1987, American Concrete Institute.All rights reserved including righs of reproduction and use in any form or byany means, including the making of copies

12、 by any photo process, or by any elect-tronic or mechanical device printed, written, or oral, or recording for sound orvisual reproduction or for we in any knowledge or retrieval system or device,unless permission in writing is obtained from the copyright proprietors.210R-1210R-2 ACI COMMITTEE REPOR

13、T5.4-Fatigue caused by vibration5.5-Materials5.6-Materials testing5.7-Construction practicesChapter 6-Control of abrasion erosion, pg. 210R-146.1-Hydraulic considerations6.2-Material evaluation6.3-MaterialsChapter 7-Control of erosion by chemical attack, pg.210R-157.1-Control of erosion by mineral-f

14、ree water7.2-Control of erosion from bacterial action7.3-Control of erosion by miscellaneous chemicalcausesPART3-MAINTENANCE AND REPAIR OF EROSIONChapter 8-Periodic inspections and corrective action,pg. 21OR-178.l-General8.2-Inspection program8.3-Inspection procedures8.4-Reporting and evaluationChap

15、ter 9-Repair methods and materials, pg . 210R-189.1-Design considerations9.2-Methods and materialsChapter 1O-References, pg. 210R-21l0.l-Specified and/or recommended references10.2-Cited referencesAppendix-Notation, pg. 210R-24PART I-CAUSES OF EROSIONCHAPTER 1-INTRODUCTIONErosion is defined in this

16、report as the progressive dis-integration of a solid by cavitation, abrasion, or chemicalaction. This report is concerned with: 1) cavitation ero-sion resulting from the collapse of vapor bubbles formedby pressure changes within a high-velocity water flow; 2)abrasion erosion of concrete in hydraulic

17、 structurescaused by water-transported silt, sand, gravel, ice, ordebris; and 3) disintegration of the concrete in hydraulicstructures by chemical attack. Other types of concretedeterioration are outside the scope of this report.Ordinarily, concrete in properly designed, constructed,used, and mainta

18、ined hydraulic structures will undergoyears of erosion-free service. However, for a variety ofreasons including inadequate design or construction, oroperational and environmental changes, erosion does oc-cur in hydraulic structures . This report deals with threemajor aspects of such concrete erosion

19、:Part 1 discusses the three major causes of concreteerosion in hydraulic structures: cavitation, abrasion, andchemical attack.FLOW ,-Vopar cavities - /Vapor cavitiesA OFFSET INTO FLOW 8. OFFSET AWAY FROM FLOW-flapor cavities - ,Vopor cavitiesC ABRUPT CURVATUREAWAY FROM FLOWD. ABRUPT SLOPEAWAY FROM F

20、LOWEr cavities- /apor cavitiesE. VOID OR TRANSVERSEG R 0 0 V EF. ROUGHENED SURFACE_Aapor cavities_i+Q+GI /-DamagePROTRUDING JOINTFig. 2.1-Cavitation situations at surface irregularitiesPart 2 discusses the options available to the designerand user to control concrete erosion in hydraulic struc-tures

21、.Part 3 discusses the evaluation of erosion problemsand provides information on repair techniques. Part 3 isnot comprehensive, and is intended as a guide for theselection of a repair method and material.CHAPTER 2-EROSION BY CAVITATION2.1-Mechanism of cavitationCavitation is the formation of bubbles

22、or cavities in aliquid. In hydraulic structures, the liquid is water, and thecavities are filled with water vapor and air. The cavitiesform where the local pressure drops to a value that willcause the water to vaporize at the prevailing fluid tem-perature. Fig. 2.1 shows examples of concrete surface

23、 ir-regularities which can trigger formation of these cavities.The pressure drop caused by these irregularities is gen-erally abrupt and is caused by local high velocities andcurved streamlines. Cavities often begin to form nearcurves or offsets in a flow boundary or at the centers ofvortices.When t

24、he geometry of flow boundaries causes stream-lines to curve or converge, the pressure will drop in thedirection toward the center of curvature or in the direc-tion along the converging streamlines. For example, Fig.2.2 shows a tunnel contraction in which a cloud of cavi-ties could start to form at P

25、oint c and then collapse atEROSION OF CONCRETE IN HYDRAULIC STRUCTURES21OR-3Fig. 2.2-Tunnel contractionPoint d. The velocity near Point c is much higher thanthe average velocity in the tunnel upstream, and thestreamlines near Point c are curved. Thus, for propervalues of flow rate and tunnel pressur

26、e at 0, the localpressure near Point c will drop to the vapor pressure ofwater and cavities will occur. Cavitation damage is pro-duced when the vapor cavities collapse. The collapsesthat occur near Point d produce very high instantaneouspressures that impact on the boundary surfaces and causepitting

27、, noise,and vibration. Pitting by cavitation isreadily distinguished from the worn appearance causedby abrasion because cavitation pits cut around the hardercoarse aggregate particles and-have irregular and roughedges.2.2-Cavitation indexThe cavitation index is a dimensionless measure usedto charact

28、erize the susceptibility of a system to cavitate.Fig. 2.2 illustrates the concept of the cavitation index. Insuch a system, the critical location for cavitation is atPoint c.The static fluid pressure at Location 1 will bewhere p, is the absolute static pressure at Point c; y isthe specific weight of

29、 the fluid (weight per unit volume);z, is the elevation at Point c; and zg is the elevation at 0.The pressure drop in the fluid as it moves along astreamline from the reference Location 0 to Location 1will bePO - IPC + Y C - %IwherepO is the static pressure at 0.The cavitation index normalizes this

30、pressure drop tothe dynamic pressure /z p vo2u=I+) - PC + Y (2, - z,)l-Eq. (2-l)/2 p v;where p is the density of the fluid (mass per unit vol-ume) and v0is the fluid velocity at 0.Readers familiar with the field of fluid mechanics mayrecognize the cavitation index as a special form of theEuler numbe

31、r or pressure coefficient, a matter discussedin Rouse (1978).If cavitation is just beginning and there is a bubble ofvapor at Point c, the pressure in the fluid adjacent to thebubble is approximately the pressure within the bubble,which is the vapor pressure pv of the fluid at the fluidstemperature.

32、Therefore, the pressure drop along the streamlinefrom 0 to 1 required to produce cavitation at the crownisand the cavitation index at the conditioncavitation isof incipient(2-2)It can be deduced from fluid mechanics considerations(Knapp, Daily, and Hammitt 1970) - and confirmed ex-perimentally - tha

33、t in a given system cavitation willbegin at a specific Us, no matter which combination ofpressure and velocity yields that uc.If the system operates at a u above uc, the system doesnot cavitate. If u is below a=, the lower the value of a,the more severe the cavitation action in a given system.Theref

34、ore, the designer should insure that the operatingu is safely above uc for the systems critical location.Actual values of uc for different systems differ mark-edly, depending on the shape of flow passages, the shapeof objects fixed in the flow, and the location wherereference pressure and velocity a

35、re measured.For a smooth surface with slight changes of slope inthe direction of flow, the value of uc may be below 0.2.For systems that produce strong vortices, uc may exceed10. Values of uc for various geometries are given inChapter 5. Falvey (1982) provides additional informationon predicting cav

36、itation in spillways.Since, in theory, a system having a given geometry willhave a certain a,- despite differences in scale, uc is auseful concept in model studies. Tullis (1981) describesmodeling of cavitation in closed circuit flow. Cavitationconsiderations (such as surface tension) in scaling fro

37、mmodel to prototype are discussed in Knapp, Daily, andHammitt (1970) and Arndt (1981).2.3-Cavitation damageCavitation bubbles will grow and travel with the flow-ing water to an area where the pressure field will causecollapse. Cavitation damage can begin at that point.When a cavitation bubble collap

38、ses or implodes close toor against a solid surface, an extremely high pressure isgenerated, which acts on an infinitesimal area of the sur-face for a very short time period. A succession of thesehigh-energy impacts will damage almost any solid mater-ial. Tests on soft metal show initial cavitation d

39、amage inthe form of tiny craters. Advanced stages of damage show21OR-4 AC1 COMMITTEE REPORTFig. 2.3-Cavitation erosion of intakelock at point of tunnel contractionwall of a navigationFig. 2.4-Christmas tree” configuration of cavitationdamage on a high-head tunnel surfacean extremely rough honeycomb

40、texture with some holesthat penetrate the thickness of the metal. This type ofpitting often occurs in pump impellers and marine pro-pellers.The progression of cavitation erosion in concrete isnot as well documented as it is in metals. For bothclasses of material, however, the erosion progressesrapid

41、ly after an initial period of exposure slightlyroughens the surface with tiny craters or pits. Possibleexplanations are that: a) the material immediately be-neath the surface is more vulnerable to attack; b) thecavitation impacts are focused by the geometry of thepits themselves; or c) the structure

42、 of the material hasbeen weakened by repeated loading (fatigue). In anyevent, the photograph in Fig. 2.3 clearly shows a ten-dency for the erosion to follow the mortar matrix andundermine the aggregate. Severe cavitation damage willtypically form a Christmas-tree configuration on spillwaychute surfa

43、ces downstream from the point of origin asshown in Fig. 2.4.Microfissures in the surface and between the mortarand coarse aggregate are believed to contribute to cavi-tation damage. Compression waves in the water that fillssuch interstices may produce tensile stresses which causemicrocracks to propa

44、gate. Subsequent compression wavescan then loosen pieces of the material. The simultaneouscollapse of all of the cavities in a large cloud, or thesupposedly slower collapse of a large vortex, quite pro-bably is capable of suddenly exerting more tha n 100 at-mospheres of pressure on an area of many s

45、quare inches.Loud noise and structural vibration attest to-the violenceof impact. The elastic rebounds from a sequence of suchblows may cause and propagate cracks and otherdamage, causing chunks of material to break loose.Fig. 2.5 shows the progress of erosion of concretedownstream from two protrudi

46、ng bolts used to generatecavitation. The tests were made at a test facility locatedat Detroit Dam, Oregon. Fig. 2.6 shows cavitationdamage on test panels after 47 hours of exposure tohigh-velocity flows in excess of 100 ft per second (ft/sec)40 meters per second (m/sec) . A large amount of cavita-ti

47、on erosion caused by a small offset at the upstreamedge of the test slab is evident.Fig. 2.7 shows severe cavitation damage that occurredto the flip bucket and training walls of an outlet structureat Lucky Peak Dam, Idaho. In this case, water velocitiesof 120 ft/sec (37 m/sec) passed through a gate

48、structureinto an open outlet manifold, part of which is shownhere. Fig. 2.8 shows cavitation damage to the side of abaffle block and the floor in the stilling basin atYellowtail Afterbay Dam, Montana.Fig. 2.5-Concretedevicestest slab fe aturin g cavitationEROSION OF CONCRETE IN HYDRAULIC STRUCTURES2

49、10R-5Fig. 2.6-Cavitation erosion pattern after 47 hours of testingat a 240 ft velocity headFig. 2.7-Cavitation erosion of discharge outlet trainingwall and flip bucketFig. 2.8-Cavitation erosion of baffle block and floor instilling basinOnce erosion has begun, the rate of erosion may beexpected to increase because protruding pieces of aggre-gate become new generators of vapor cavities. In fact, acavity cloud often is caused by the change in direction ofFig. 3.1-Abrasion damage to concrete baffle blocks andfloor area in Yellowtail Diversion Dam sluiceway, Montanathe boundary at the