1、Report on the Erosion of Concrete in Hydraulic Structures Reported by ACI Committee 207 ACI 207.6R-17First Printing September 2017 ISBN: 978-1-945487-79-8 Report on the Erosion of Concrete in Hydraulic Structures Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved
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11、ly revised ACI Manual of Concrete Practice (MCP). American Concrete Institute 38800 Country Club Drive Farmington Hills, MI 48331 Phone: +1.248.848.3700 Fax: +1.248.848.3701 www.concrete.orgThis report outlines the causes, control, maintenance, and repair of erosion in hydraulic structures. Such ero
12、sion occurs from three major causes: cavitation, abrasion, and chemical attack. Design parameters, materials selection and quality, environmental factors, and other issues affecting the performance of concrete are discussed. Evidence exists to suggest that, given the operating characteris- tics and
13、conditions to which a hydraulic structure will be subjected, the concrete can be designed to mitigate future erosion. However, when operational factors change or are not clearly known and erosion of concrete surfaces occurs, repairs should follow. This report addresses the subject of concrete erosio
14、n, inspection tech- niques, and repair strategies, providing references to a more detailed treatment of the subject. Keywords: abrasion; aeration; cavitation; chemical attack; concrete dams; corrosion; erosion; hydraulic structures; spillways. CONTENTS CHAPTER 1INTRODUCTION AND SCOPE, p. 2 1.1Introd
15、uction, p. 2 1.2Scope, p. 2 CHAPTER 2NOTATION, p. 2 2.1Notation, p. 2 CHAPTER 3EROSION BY CAVITATION, p. 3 3.1Mechanism of cavitation, p. 3 3.2Cavitation index, p. 3 3.3Cavitation damage, p. 4 CHAPTER 4EROSION BY ABRASION, p. 6 4.1General, p. 6 4.2Stilling basin damage, p. 6 John W. Gajda, Chair Chr
16、istopher C. Ferraro, Secretary ACI 207 .6R-17 Report on the Erosion of Concrete in Hydraulic Structures Reported by ACI Committee 207 Fares Y . Abdo Oscar R. Antommattei Terrence E. Arnold Katie J. Bartojay * Teck L. Chua Timothy P. Dolen Darrell Elliot Barry D. Fehl Mario Garza Melissa O. Harrison
17、Michael G. Hernandez James K. Hicks Rodney E. Holderbaum Ronald L. Kozikowski Tibor J. Pataky Jonathan L. Poole Henry B. Prenger Ernest A. Rogalla Ernest K. Schrader Kuntay K. Talay Nathaniel F. Tarbox Stephen B. Tatro Michael A. Whisonant Fouad H. Yazbeck Consulting Members Jeffrey C. Allen Randall
18、 P. Bass Anthony A. Bombich Robert W. Cannon Eric J. Ditchey Brian A. Forbes Allen J. Hulshizer Richard A. Kaden William F. Kepler David E. Kiefer * Primary author of this report. Deceased. Committee 207 would like to thank the following individuals for their contribution to this report: J. Ballenti
19、ne, J. F. Best, G. Mass, W. McEwen, M. Petrovsky, and M. Stegallo. ACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the signific
20、ance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising
21、 therefrom. Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer. ACI 207.6R-17 supers
22、edes ACI 210R-93(08) and was adopted and published September 2017. Copyright 2017, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device, printe
23、d, written, or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. 14.3Power plant tailrace damage, p. 7 4.4Navigation lock damage, p. 8 4.5Tunnel lining damage, p. 8 4
24、.6Hydraulic jacking, p. 8 CHAPTER 5EROSION BY CHEMICAL ATTACK, p. 9 5.1Sources of external chemical attack, p. 9 5.2Erosion by mineral-free water, p. 9 5.3Erosion by miscellaneous causes, p. 9 CHAPTER 6CONTROL OF CAVITATION EROSION, p. 10 6.1Hydraulic design principles, p. 10 Example 1, p. 10 6.2Cav
25、itation indexes for damage and construction tolerances, p. 11 Example 2, p. 11 6.3Using aeration to control damage, p. 12 6.4Materials, p. 13 6.5Materials testing, p. 14 6.6Construction practices, p. 14 CHAPTER 7CONTROL OF ABRASION EROSION, p. 15 7.1Hydraulic considerations, p. 15 7.2Materials evalu
26、ation, p. 16 7.3Materials, p. 16 CHAPTER 8CONTROL OF EROSION BY CHEMICAL ATTACK, p. 17 8.1Control of erosion by mineral-free water, p. 17 8.2Control of erosion from acid attack due to bacterial action, p. 18 8.3Control of erosion by miscellaneous chemical causes, p. 18 CHAPTER 9PERIODIC INSPECTIONS
27、AND CORRECTIVE ACTION, p. 19 9.1General, p. 19 9.2Inspection program, p. 19 9.3Inspection procedures, p. 19 9.4Reporting and evaluation, p. 19 CHAPTER 10REPAIR METHODS AND MATERIALS, p. 20 10.1Design considerations, p. 20 10.2Methods and materials, p. 20 CHAPTER 11REFERENCES, p. 22 Authored document
28、s, p. 23 CHAPTER 1INTRODUCTION AND SCOPE 1.1Introduction Erosion is the progressive disintegration of a solid by: 1) cavitation; 2) abrasion; or 3) chemical action. Although concrete deteriorates for a variety of reasons, this report is concerned with specific factors that influence these three area
29、s of erosion: 1) cavitation-erosion resulting from the collapse of vapor bubbles formed by pressure changes within a high-velocity water flow; 2) abrasion-erosion of concrete in hydraulic structures caused by water-transported silt, sand, gravel, ice, debris, or hydraulic jacking; and 3) chemical ac
30、tion-disintegration of the concrete in hydraulic structures by chemical attack. Concrete in properly designed, constructed, used, and maintained hydraulic structures can provide 30 to 50 years of erosion-free service (Liu and Wang 2000). However, for reasons including inadequate design or constructi
31、on, or operational and environmental changes, erosion does occur in hydraulic structures. 1.2Scope Concrete erosion in hydraulic structures caused by cavi- tation, abrasion, and chemical attack are included in this report. Options available to the designer and user to control concrete erosion in hyd
32、raulic structures are discussed, along with information on the inspection and evaluation of erosion problems. This report includes repair techniques, as well as a brief guide to methods and materials for repair. Other types of concrete deterioration are outside the scope of this report. CHAPTER 2NOT
33、ATION 2.1Notation F = force l = length of air space between the jet and the spillway floor, ( = length) p = water pressure at a given point, F/ 2 p 0= absolute pressure at a given Point 0, F/ 2 p c= absolute pressure at a given Point c, F/ 2 p v= vapor pressure of water, F/ 2 q a= volume rate of air
34、 entrainment per unit width of jet, 3 /T q d= amount of air a turbulent jet will entrain along its lower surface, 3 /T T = time v = average jet velocity at midpoint of trajectory, /T v 0= average velocity at Section 0, /T Y 0= offset into the flow, z 0= elevation at centerline of pipe, z c= elevatio
35、n of the vapor bubble, = width of jet coefficient based on turbulent intensity of the jet p = change in pressure between two points, F/ 2 = specific weight of water, F/ 3(62.4 lb/ft 39.81 kN/ m 3 , temperature-dependent = mass density of water, FT 2 / 4(1.94 lbs 2 /ft 41000 kg/m 3 , temperature-depe
36、ndent) = cavitation index c= value of cavitation index at which cavitation initiates American Concrete Institute Copyrighted Material www.concrete.org 2 REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTURES (ACI 207 .6R-17)CHAPTER 3EROSION BY CAVITATION 3.1Mechanism of cavitation Cavitation is t
37、he formation of bubbles or cavities in a liquid. In hydraulic structures, the liquid is water, and the cavities are filled with water vapor and air. The cavities form where the local pressure drops to a value that will cause the water to vaporize at the prevailing fluid temperature. Figure 3.1a show
38、s examples of concrete surface irregulari- ties that can trigger formation of these cavities. The pressure drop caused by these irregularities is generally abrupt and is caused by local high velocities and curved streamlines. Cavities often begin to form near curves or offsets in a flow boundary or
39、at the centers of vortexes. When the geometry of flow boundaries causes streamlines to curve or converge, the pressure may drop in the direc- tion toward the center of curvature or in the direction along the converging streamlines. For example, Fig. 3.1b shows a tunnel contraction in which a cloud o
40、f cavities could start to form at Point (c) and then collapse at Point (d). The velocity near Point (c) is much higher than the average velocity in the tunnel upstream, and the streamlines near Point (c) are curved. Thus, for proper values of flow rate and tunnel pres- sure at Point (0), the local p
41、ressure near Point (c) drops to the vapor pressure of water and cavities will occur. Cavitation damage is produced when the vapor cavities collapse. The collapses that occur near Point (d) produce high instanta- neous pressures that impact on the boundary surfaces and cause pitting, noise, and vibra
42、tion. Pitting by cavitation is readily distinguished from the worn appearance caused by abrasion because cavitation pits cut around the harder coarse aggregate particles and have irregular and rough edges. 3.2Cavitation index The cavitation index is a dimensionless measure used to characterize the s
43、usceptibility of a system to cavitate. Figure 3.2 illustrates the design principle of the cavitation index in a tunnel contraction. In such a system, the critical location (or point) for cavitation is at Point (c) (Fig. 3.1b). The static fluid pressure, where the velocity is essentially the same as
44、the approach velocity, at Point (1) will bep 1= p c+ (z c z 0 ) (3.2a) where p cis the absolute static pressure at Point (c); is the specific weight of the fluid (weight per unit volume); z cis the elevation at Point (c); and z 0is the elevation at Point (0). The pressure drop in the fluid as it mov
45、es along a stream- line from the reference Point (0) to Point (1) will be p = p 0 p c+ (z c z 0 ) (3.2b) where p 0is the static pressure at Point (0). The cavitation index normalizes this pressure drop to the dynamic pressure. Dynamic pressure is the difference between the total pressure (pressure a
46、t the point of stagna- tion) and the static pressure, 1/2v 0 2(Eq. (3.2b). (3.2c) where is the density of the fluid (mass per unit volume), and v 0is the fluid velocity at Point (0). Readers familiar with the field of fluid mechanics may recognize the cavitation index as a special form of the Euler
47、number or pressure coefficient, a matter discussed in Rouse (1978). If cavitation is just beginning and there is a bubble of vapor at Point (c), the pressure in the fluid adjacent to the bubble is approximately the pressure within the bubble, which is the vapor pressure p vof the fluid at the fluids
48、 temperature. Therefore, the pressure drop along the flow from Point (0) to (1) required to produce cavitation at the crown is p = p v p c+ (z c z 0 ) Fig. 3.1aCavitation situations at surface irregularities (Falvey 1990). Fig. 3.1bTunnel contraction. American Concrete Institute Copyrighted Material
49、 www.concrete.orgREPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTURES (ACI 207 .6R-17) 3and the cavitation index at the condition of incipient cavita- tion is (3.2d) It can be deduced from fluid mechanics considerations (Knapp et al. 1970), and confirmed experimentally, that in a given system, cavitation will begin at a specific c , no matter which combination of pressure and velo
