1、Designation: D 5243 92 (Reapproved 2007)Standard Test Method forOpen-Channel Flow Measurement of Water Indirectly atCulverts1This standard is issued under the fixed designation D 5243; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the computation of discharge(the volume rate of flow) of water in open channels
3、 or streamsusing culverts as metering devices. In general, this test methoddoes not apply to culverts with drop inlets, and applies only toa limited degree to culverts with tapered inlets. Informationrelated to this test method can be found in ISO 748 andISO 1070.1.2 This test method produces the di
4、scharge for a floodevent if high-water marks are used. However, a completestage-discharge relation may be obtained, either manually orby using a computer program, for a gauge located at theapproach section to a culvert.1.3 The values stated in inch-pound units are to be regardedas the standard. The
5、SI units given in parentheses are forinformation only.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 health practices and determine the applica-bility
6、of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD 3858 Test Method for Open-Channel Flow Measurementof Water by Velocity-Ar
7、ea Method2.2 ISO Standards:3ISO 748 Liquid Flow Measurements in Open Channels-Velocity-Area MethodsISO 1070 Liquid Flow Measurements in Open Channels-Slope-Area Methods3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129.3.2 Definitions of Terms
8、Specific to This StandardSeveralof the following terms are illustrated in Fig. 1:3.2.1 alpha (a)a velocity-head coefficient that adjusts thevelocity head computed on basis of the mean velocity to thetrue velocity head. It is assumed equal to 1.0 if the cross sectionis not subdivided.3.2.2 conveyance
9、 (K)a measure of the carrying capacityof a channel and having dimensions of cubic feet per second.3.2.2.1 DiscussionConveyance is computed as follows:K 51.486nR2/3Awhere:n = the Manning roughness coefficient,A = the cross section area, in ft2(m2), andR = the hydraulic radius, in ft (m).3.2.3 cross s
10、ections (numbered consecutively in down-stream order):3.2.3.1 The approach section, Section 1, is located oneculvert width upstream from the culvert entrance.3.2.3.2 Cross Sections 2 and 3 are located at the culvertentrance and the culvert outlet, respectively.3.2.3.3 Subscripts are used with symbol
11、s that representcross sectional properties to indicate the section to which theproperty applies. For example, A1is the area of Section 1.Items that apply to a reach between two sections are identified1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsi
12、bility of Subcommittee D19.07 on Sediments, Geomor-phology, and Open-Channel Flow.Current edition approved June 15, 2007. Published July 2007. Originallyapproved in 1992. Last previous edition approved in 2001 as D 5243 92 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org,
13、orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Cop
14、yright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.by subscripts indicating both sections. For example, hf12is thefriction loss between Sections 1 and 2.3.2.4 cross sectional area (A)the area occupied by thewater.3.2.5 energy loss (hf)the l
15、oss due to boundary frictionbetween two locations.3.2.5.1 DiscussionEnergy loss is computed as follows:hf5 L SQ2K1K2Dwhere:Q = the discharge in ft3/s (m3/s), andL = the culvert length in ft (m).3.2.6 Froude number (F)an index to the state of flow inthe channel. In a rectangular channel, the flow is
16、subcritical ifthe Froude number is less than 1.0, and is supercritical if it isgreater than 1.0.3.2.6.1 DiscussionThe Froude number is computed asfollows:F 5V= gdmwhere:V = the mean velocity in the cross section, ft/s (m/s),dm= the average depth in the cross section, in ft (m), andg = the accelerati
17、on due to gravity (32 ft/s2) (9.8 m/s2).3.2.7 high-water marksindications of the highest stagereached by water including, but not limited to, debris, stains,foam lines, and scour marks.3.2.8 hydraulic radius (R)the area of a cross section orsubsection divided by the wetted perimeter of that section
18、orsubsection.3.2.9 roughness coeffcient (n)Mannings n is used in theManning equation.3.2.10 velocity head (hv)is computed as follows:hv5aV22gwhere:a = the velocity-head coefficient,V = the mean velocity in the cross section, in ft/s (m/s), andg = the acceleration due to gravity, in ft/s/s (m/s/s).3.
19、2.11 wetted perimeter (WP)the length along the bound-ary of a cross section below the water surface.4. Summary of Test Method4.1 The determination of discharge at a culvert, either aftera flood or for selected approach stages, is usually a reliablepractice. A field survey is made to determine locati
20、ons andelevations of high-water marks upstream and downstream fromthe culvert, and to determine an approach cross section, and theculvert geometry. These data are used to compute the eleva-tions of the water surface and selected properties of thesections. This information is used along with Mannings
21、 n inthe Manning equation for uniform flow and discharge coeffi-cients for the particular culvert to compute the discharge, Q,incubic feet (metres) per second.5. Significance and Use5.1 This test method is particularly useful to determine thedischarge when it cannot be measured directly with some ty
22、peof current meter to obtain velocities and sounding equipment todetermine the cross section. See Practice D 3858.5.2 Even under the best of conditions, the personnel avail-able cannot cover all points of interest during a major flood.The engineer or technician cannot always obtain reliableresults b
23、y direct methods if the stage is rising or falling veryrapidly, if flowing ice or debris interferes with depth or velocitymeasurements, or if the cross section of an alluvial channel isscouring or filling significantly.5.3 Under flood conditions, access roads may be blocked,cableways and bridges may
24、 be washed out, and knowledge ofthe flood frequently comes too late. Therefore, some type ofindirect measurement is necessary. The use of culverts todetermine discharges is a commonly used practice.NOTE 1The loss of energy near the entrance is related to the sudden contraction and subsequent expansi
25、on of the live stream within the culvert barrel.FIG. 1 Definition Sketch of Culvert FlowD 5243 92 (2007)26. Apparatus6.1 The equipment generally used for a “transit-stadia”survey is recommended. An engineers transit, a self-levelinglevel with azimuth circle, newer equipment using electroniccircuitry
26、, or other advanced surveying instruments may beused. Necessary equipment includes a level rod, rod level, steeland metallic tapes, survey stakes, and ample note paper.6.2 Additional items of equipment that may expedite asurvey are tag lines (small wires with markers fixed at knownspacings), vividly
27、 colored flagging, axes, shovels, hip boots orwaders, nails, sounding equipment, ladder, and rope.6.3 Acamera should be available to take photographs of theculvert and channel. Photographs should be included with thefield data.6.4 Safety equipment should include life jackets, first aidkit, drinking
28、water, and pocket knives.7. Sampling7.1 Sampling as defined in Terminology D 1129 is notapplicable in this test method.8. Calibration8.1 Check adjustment of surveying instruments, transit, etc.,daily when in continuous use or after some occurrence thatmay have affected the adjustment.8.2 The standar
29、d check is the “two-peg” or “double-peg”test. If the error is over 0.03 in 100 ft (0.091 m in 30.48 m),adjust the instrument. The two-peg test and how to adjust theinstrument are described in many surveying textbooks. Refer tomanufacturers manual for the electronic instruments.8.3 The “reciprocal le
30、veling” technique (1)4is consideredthe equivalent of the two-peg test between each of twosuccessive hubs.8.4 Visually check sectional and telescoping level rods atfrequent intervals to be sure sections are not separated. Aproper fit at each joint can be checked by measurements acrossthe joint with a
31、 steel tape.8.5 Check all field notes of the transit-stadia survey beforeproceeding with the computations.9. Description of Flow at Culverts9.1 Relations between the head of water on and dischargethrough a culvert have been the subjects of laboratory inves-tigations by the U.S. Geological Survey, th
32、e Bureau of PublicRoads, the Federal HighwayAdministration, and many univer-sities. The following description is based on these studies andfield surveys at sites where the discharge was known.9.2 The placement of a roadway fill and culvert in a streamchannel causes an abrupt change in the character
33、of flow. Thischannel transition results in rapidly varied flow in whichacceleration due to constriction, rather than losses due toboundary friction, plays the primary role. The flow in theapproach channel to the culvert is usually tranquil and fairlyuniform. Within the culvert, however, the flow may
34、 be sub-critical, critical, or supercritical if the culvert is partly filled, orthe culvert may flow full under pressure.9.2.1 The physical features associated with culvert flow areillustrated in Fig. 1. They are the approach channel crosssection at a distance equivalent to one opening width upstrea
35、mfrom the entrance; the culvert entrance; the culvert barrel; theculvert outlet; and the tailwater representing the getawaychannel.9.2.2 The change in the water-surface profile in the ap-proach channel reflects the effect of acceleration due tocontraction of the cross-sectional area. Loss of energy
36、near theentrance is related to the sudden contraction and subsequentexpansion of the live stream within the barrel, and entrancegeometry has an important influence on this loss. Loss ofenergy due to barrel friction is usually minor, except in longrough barrels on mild slopes. The important features
37、thatcontrol the stage-discharge relation at the approach section canbe the occurrence of critical depth in the culvert, the elevationof the tailwater, the entrance or barrel geometry, or a combi-nation of these.9.2.3 Determine the discharge through a culvert by applica-tion of the continuity equatio
38、n and the energy equationbetween the approach section and a control section within theculvert barrel. The location of the control section depends onthe state of flow in the culvert barrel. For example: If criticalflow occurs at the culvert entrance, the entrance is the controlsection, and the headwa
39、ter elevation is not affected by condi-tions downstream from the culvert entrance.10. General Classification of Flow10.1 Culvert Flow Culvert flow is classified into six typeson the basis of the location of the control section and therelative heights of the headwater and tailwater elevations toheigh
40、t of culvert. The six types of flow are illustrated in Fig. 2,and pertinent characteristics of each type are given in Table 1.10.2 Definition of HeadsThe primary classification offlow depends on the height of water above the upstream invert.This static head is designated as h1 z, where h1is the heig
41、htabove the downstream invert and z is the change in elevation ofthe culvert invert. Numerical subscripts are used to indicate thesection where the head was measured. A secondary part of theclassification, described in more detail in Section 18, dependson a comparison of tailwater elevation h4to the
42、 height of waterat the control relative to the downstream invert. The height ofwater at the control section is designated hc.10.3 General ClassificationsFrom the information in Fig.2, the following general classification of types of flow can bemade:10.3.1 If h4/D is equal to or less than 1.0 and (h1
43、 z)/D isless than 1.5, only Types 1, 2 and 3 flow are possible.10.3.2 If h4/D and (h1 z)/D are both greater than 1.0, onlyType 4 flow is possible.10.3.3 If h4/D is equal to or less than 1.0 and (h1 z)/D isequal to or greater than 1.5, only Types 5 and 6 flow arepossible.10.3.4 If h4/D is equal to or
44、 greater than 1.0 on a steepculvert and (hz z)/D is less than 1.0, Types 1 and 3 flows arepossible. Further identification of the type of flow requires a4The boldface numbers in parentheses refer to a list of references at the end ofthe text.D 5243 92 (2007)3trial-and-error procedure that takes time
45、 and is one of thereasons use of the computer program is recommended.11. Critical Depth11.1 Specific EnergyIn Type 1 flow, critical depth occursat the culvert inlet, and inType 2 flow critical flow occurs at theculvert outlet. Critical depth, dc, is the depth of water at thepoint of minimum specific
46、 energy for a given discharge andcross section. The relation between specific energy and depth isillustrated in Fig. 3. The specific energy, Ho, is the height of theenergy grade line above the lowest point in the cross section.Thus:Ho5 d 1V22gwhere:Ho= specific energy,d = maximum depth in the sectio
47、n, in ft,V = mean velocity in the section, in ft/s, andg = acceleration of gravity (32 ft/s2) (9.8 m/s2).11.2 Relation Between Discharge and DepthIt can beshown that at the point of minimum specific energy, that is, atcritical depth, dc, there is a unique relation between discharge(or velocity) and
48、depth as shown by the following equations:Q2g5A3Tand:V2g5 dm5ATwhere:Q = discharge, in ft3/s (m3/s),A = area of cross section below the water surface,ft2(m2),T = width of the section at the water surface, in ft (m),dc= maximum depth of water in the critical-flow sec-tion, in ft (m), anddm= mean dept
49、h in section = A/T, in ft (m).Therefore, assuming either depth of discharge fixes the other.The computational procedures utilize trial iterations wherecritical depth is assumed and the resultant discharge is used asa trial value for computing energy losses, which are in turnFIG. 2 Classification of Culvert FlowTABLE 1 Characteristics of Flow TypesNOTE 1D = maximum vertical height of barrel and diameter of circular culverts.Flow Type Barrel FlowLocation ofTerminal SectionKind of Control Culvert Slopeh12 zDh4hch4D1 Partly full Inlet Critical depth St
