1、Designation: D 7276 08Standard Guide forAnalysis and Interpretation of Test Data for ArticulatingConcrete Block (ACB) Revetment Systems in Open ChannelFlow1This standard is issued under the fixed designation D 7276; the number immediately following the designation indicates the year oforiginal adopt
2、ion or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 The purpose of this guide is to provide recommendedguidelines for the ana
3、lysis and interpretation of hydraulic testdata for articulating concrete block (ACB) revetment systemsunder steep slope, high velocity flow conditions in a rectangu-lar open channel. Data from tests performed under controlledlaboratory conditions are used to quantify stability perfor-mance of ACB sy
4、stems under hydraulic loading. This guide isintended to be used in conjunction with Test Method D 7277.1.2 This guide offers an organized collection of informationor a series of options and does not recommend a specific courseof action. This document cannot replace education or experi-ence and shoul
5、d be used in conjunction with professionaljudgment. Not all aspects of this guide may be applicable in allcircumstances. This ASTM standard is not intended to repre-sent or replace the standard of care by which adequacy of agiven professional service must be judged, nor can thisdocument be applied w
6、ithout considerations of a projectsmany unique aspects. The word “Standard” in the title of thisdocument means only that the document has been approvedthrough the ASTM consensus process.1.3 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathe
7、maticalconversions to SI units that are provided for information onlyand are not considered standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and hea
8、lth practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 6684 Specification for Materials and Manufacture ofArticulating Concrete Block (ACB) Revetment SystemsD 6884
9、 Practice for Installation of Articulating ConcreteBlock (ACB) Revetment SystemsD 7277 Test Method for Determining Hydraulic Stability ofArticulating Concrete Block Revetment Systems in OpenChannel Flow3. Terminology3.1 For definitions of terms used in this standard, seeTerminology D 653.4. Summary
10、of Guide4.1 The analysis and interpretation of data from hydraulictests of articulating concrete block (ACB) revetment systems isessential to the selection and design of a suitable system for aspecific application. This guide provides guidelines for assist-ing designers and specifiers in developing
11、a correspondencebetween the test data and the stability parameters used fordesign.4.2 This standard addresses the analysis of hydraulic testdata that is generated from a test or series of tests conducted inaccordance with Test Method D 7277.5. Significance and Use5.1 This standard is intended for us
12、e by researchers anddesigners to assess the stability of articulating concrete block(ACB) revetment systems in order to achieve stable hydraulicperformance under the erosive force of flowing water.5.2 An articulating concrete block system is comprised of amatrix of individual concrete blocks placed
13、together to form anerosion-resistant revetment with specific hydraulic perfor-mance characteristics. The system includes a filter layercompatible with the subsoil which allows infiltration andexfiltration to occur while providing particle retention. Thefilter layer may be comprised of a geotextile,
14、properly gradedgranular media, or both. The blocks within the matrix shall bedense and durable, and the matrix shall be flexible and porous.1This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.25 on Erosion and SedimentContro
15、l Technology.Current edition approved Aug. 1, 2008. Published September 2008.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page ont
16、he ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 Articulating concrete block systems are used to provideerosion protection to underlying soil materials from the forcesof flowing water. The term “articulating,” as u
17、sed in thisstandard, implies the ability of individual blocks of the systemto conform to changes in the subgrade while remaininginterconnected by virtue of block interlock or additional systemcomponents such as cables, ropes, geotextiles, geogrids, orother connecting devices, or combinations thereof
18、.5.4 The definition of articulating concrete block systemsdoes not distinguish between interlocking and non-interlockingblock geometries, between cable-tied and non-cable-tied sys-tems, between vegetated and non-vegetated systems or be-tween methods of manufacturing or placement. This standarddoes n
19、ot specify size restrictions for individual block units.Block systems are available in either open-cell or closed-cellvarieties.6. Procedure6.1 Data Analysis:6.1.1 This section describes the analysis and interpretationof the data collected during a test, including the determinationof hydraulic condi
20、tions, qualitative observations and descrip-tions of any damage to the revetment system, and quantifica-tion of threshold hydraulic stability values that are character-istic of the tested system.6.1.2 Typical test environments incorporate a flow regimethat is supercritical, characterized by high vel
21、ocities withrelatively shallow depths of flow. In supercritical flow, smallvariations in measured depth can result in relatively largevariations in calculated energy and shear stress. The analyticalmethods suggested in this section have been selected based ontheir suitability to analyze these hydrau
22、lic conditions.6.2 Hydraulic Conditions:6.2.1 Accurately quantifying the hydraulic conditions thatexisted during the test is fundamental to the establishment ofstability performance thresholds. The important hydraulic vari-ables that characterize open channel flow include total dis-charge Q, section
23、-averaged velocity V, flow depth y, slope ofthe energy grade line Sf, resistance coefficient (for example,Manning n-value), and boundary shear stress t.6.2.2 Total Discharge, Q, is determined by use of a primaryflow measurement device such as an in-line flow meter, weir,Parshall flume, or other devi
24、ce appropriate to the facilitysmeans for delivering water to the test section.Alternatively, thedischarge may be computed at each of the measurementcross-sections by the continuity equation:Q 5 AV0.6! (1)where:V0.6= centerline point velocity at six-tenths of the depth offlow at each station, ft/s (m
25、/s), andA = the cross-sectional area of flow at the same station,measured perpendicular to the direction of flow,ft2(m2).6.2.2.1 The accuracy of the discharge measurement shall bereported as described in Section 7 of this standard.6.2.3 Flow Depth, y, is computed as the difference in themeasured cen
26、terline water surface elevation and the elevationof the revetment surface, corrected for the slope angle u asappropriate, at each measurement station:yi5 hi zi! cos u (2)where:yi= depth of flow at station i (perpendicular to the bed), ft(m),hi= water surface elevation at station i, ft (m),zi= bed el
27、evation (top of blocks) at station i, ft (m), andu = slope angle measured from the horizontal.6.2.4 Energy Grade Slope, Sf, at each measurement stationis calculated from other measured or computed variables as:Sfi5FnVi!KuG21yi4/3(3)where:Sfi= slope of the energy grade line at station i, ft/ft (m/m),
28、n = Mannings resistance coefficient,Vi= velocity at station i, ft/s (m/s), andKu= units conversion coefficient, equal to 1.486 for U.S.Customary Units and 1.0 for SI Units.6.2.4.1 Eq 3 assumes that the flume walls are significantlysmoother than the revetment surface, such that the totalresistance is
29、 due solely to the roughness of the bed.6.2.5 Step-Forewater AnalysisKnowing the total dis-charge Q, flume width b, and the elevations of the watersurface and revetment surface at each of the measurementstations, a forewater calculation can be performed to obtain theoptimal value of the Mannings n c
30、oefficient.6.2.5.1 For supercritical flow, it is recommended that thewater surface profile be computed by solving the momentumequation using the standard step method and proceeding in thedownstream direction:h25 h1112gv11 v2! v1 v2! L2Sf11 Sf2! (4)where:h1,h2= upstream and downstream water surface e
31、leva-tions at stations 1 and 2, ft (m),v1,v2= upstream and downstream velocity at stations 1and 2, ft/s (m/s),L = slope length between stations 1 and 2, ft (m),andSf1,Sf2= upstream and downstream energy grade slopesat stations 1 and 2 as defined by Eq 3, ft/ft(m/m).NOTE 1Other numerical methods are
32、available for computing thewater surface profile, for example the direct step method. The standardstep method is being recommended here because it allows computation ofhydraulic conditions at the actual locations of the flume measurementstations.6.2.5.2 The objective function to be minimized is defi
33、nedas:j5(i5i1inabshpred hobs! (5)where:i1= beginning station for analysis,in= ending station for analysis,D7276082hpred= predicted water surface elevation at station ii,ft(m), andhobs= observed water surface elevation at station ii,ft(m).6.2.5.3 By examining a range of Mannings n values, theoptimal
34、Mannings n is identified as that which yields theminimum value of the objective function defined by Eq 5. Theoptimal Mannings n value is then used to calculate the watersurface elevation that best fits the observed data. An exampleof such a forewater calculation is provided in Annex A1.6.2.6 Section
35、-Average Velocity, Vave, is computed as dis-charge Q (determined above) divided by the cross-sectionalarea A, normal to the embankment surface, at each measure-ment station along the test section.6.2.7 Energy Grade Line Elevation, EGL, is determined ateach measurement station by the following equati
36、on:EGLi5 zi1 yicos u! 1Vi!22g(6)where:EGLi= elevation of the energy grade line at station i,ft(m), andg = gravitational constant, 32.2 ft/s2(9.81 m/s2).6.2.7.1 The procedure for determining energy slope shouldbe performed for the data representing the flow field on thedownstream slope of the test se
37、ction. If a measurement stationhappens to coincide with the point of the break in slope, datafrom that station should not be used because of the severe flowcurvature at that location.6.2.8 Shear Stress, t0If gradually varied flow character-izes the flow field, the maximum boundary shear stress at th
38、ebed, t0, is determined from measured or calculated variablesas:t05gy! Sf! (7)where:t0= bed shear stress, lb/ft2(N/m2),g = unit weight of water, 62.4 lb/ft3(9,810 N/m3),y = depth of flow measured perpendicular to the bed, ft(m), andSf= slope of energy grade line as defined by Eq 3.6.2.8.1 The above
39、equation requires the use of representa-tive data from two or more stations on the downstream slope todetermine the slope of the energy grade line Sf, and therepresentative depth associated with that determination. Typi-cally, a linear regression is performed to determine the slope ofthe energy grad
40、e line. The measured depths from the stationsused in this regression analysis are averaged to determine therepresentative depth y in order to calculate the bed shear stress.6.2.8.2 Alternatively, the momentum equation across a rep-resentative control volume of finite length L may be used tocalculate
41、 t0:t05g2y11 y2! sin u11LFg2y12 y22! cos u rq2S1y21y1DG(8)where:g = unit weight of water, 62.4 lb/ft3(9810 N/m3),y1,y2= flow depths at the upstream and downstream endsof the control volume, respectively, ft (m),v1,v2= flow velocity at the upstream and downstreamends of the control volume, respective
42、ly, ft/s(m/s),L = length of the control volume along the slope, ft(m),r = unit mass of water, 1.94 slugs/ft3(1000 kg/m3),andq = unit discharge, ft3/s per foot width (m3/s per meterwidth).6.2.8.3 Both methods given above for quantifying shearstress depend on the judgment of the practitioner to define
43、 thedata that best represents the stable performance of the blocksystem. In practice, many data sets will include one or morepoints where the energy grade is not consistent with theexpected trend. In most cases, outliers can be most readilyidentified by plotting the elevation of the energy line vers
44、usdistance along the embankment. Note that when Eq 8 is used,the x-axis plotting position for the calculated shear stress t0islocated halfway between stations 1 and 2.6.2.8.4 Annex A1 provides an example of such a plot, andillustrates the use of the step-forewater analysis procedure toquantify the h
45、ydraulic conditions in areas where data variabil-ity exists. Fig. 1 provides a definition sketch for the variablespresented in this section.6.3 Qualitative Observations of Stability:6.3.1 The hydraulic conditions at the threshold of failuredetermine the hydraulic stability parameters that characteri
46、zethe revetment systems performance. Both shear stress andvelocity at the threshold of failure are typically used forpurposes of developing selection and design criteria for aparticular block system.6.3.2 The researchers determination of “failure” of a revet-ment system during a test is somewhat sub
47、jective, and dependson his interpretation of the point on the embankment at which“loss of intimate contact” between the revetment system andthe subgrade soil occurred. In practice, all of the followingconditions have been used as guidance for this interpretation(listed in decreasing order of frequen
48、cy of occurrence):6.3.2.1 Vertical displacement or loss of a block (or group ofblocks).6.3.2.2 Loss of soil beneath the geotextile, resulting invoids.6.3.2.3 Liquefaction and mass slumping/sliding of the sub-soil.3, 4, 53Chen, Y. H., and Anderson, B. A., “Development of a Methodology forEstimating E
49、mbankment Damage due to Flood Overtopping,” Final Report, Simons,Li channel stability; erosion;erosion control; open channel flow; overtopping; revetmentFIG. 1 Definition SketchD7276084ANNEX(Mandatory Information)A1. STEP-FOREWATER PROGRAM FOR CALCULATING SUPERCRITICAL FLOW IN OPEN CHANNELSA1.1 The following example uses the standard-step methodfor solving the momentum equation presented in Section 6 ofthis standard. The method assumes that Mannings equation isvalid for describing gradually varied flow in the section to beanalyzed.6The iterative proced
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