hydraulic design criteria us army

HYDRAULIC DESIGN CRITERIA

SHEET 703-1

RIPRAP PROTECTION

TRAPEZOIDAL CHANNEL, 60 DEG-BEND

1. Riprap used

BOUNDARY SHEAR DISTRIBUTION

to aid in the stabilization of natural streams andartificial channels is most comonly placed in the vicinity of bends.Procedures for estimating the required size of riprap in straight chan-nels have been presented by the U. S. Army Engineer Waterways ExperimentStationl and Office, Chief of Engineers.2 No similar procedure has beendeveloped for evaluating riprap size for channel bends. Hydraulic DesignChart 703-1 is based on laboratory tests at the Massachusetts Instituteof Technology (ltIT)3and should be useful for estimating relative boundaryshear distribution in simple channel bends having trapezoidal cross sec-tions, moderate side slopes, and approximately 60-deg deflection angles.It may also serve as a general guide for riprap gradation in natural chan-nel bends of similar geometry. Shear distribution diagrams for other bendgeometries and flow conditions have been published.s~h

2. Laboratory studies of boundary shear in open channel bends oftrapezoidal cross sections~j indicate that the highest boundary shearcaused by the bend geometry occurs immediately downstream from the bendand along the outside bank. Another area of high boundary shear is lo-cated at the inside of the bend. The relative boundary shear distribu-tion in a simple bend with a rough boundary is given in Chart 703-1. Thechart is based on fig. 21 of the MIT reports

3. Experimental Data. Laboratory tests on smooth channel bendshave been mad? at MIT,~ at U. S. Bureau of Reclamation,5 and at the Univer-sity of Iowa.b In addition, limited tests on rough channel bends have beenmade at MIT. In the latter tests, the channel was roughened by fixing0.18- by 0.10- by O.10-in. parallelepipeds to the boundary in a randommanner which resulted in an absolute roughness height of 0.10 in. The MITtest channel was 24 in. wide with L on 2 side slopes. The boundary sheardistribution pattern has been generally found to be the same in all.testson simple curves having smooth and rough boundary conditions. However,the magnitude of the ratio of bend local boundary shear to the averageboundary shear in the approach channel appears to be a’function of thechannel and bend geometry. Some work has also been done at MIT3 on boundaryshear distribution in double and reverse curve channels.

4. Application. Extensive variation in riprap gradation throughouta bend may not be practical or economical. However, increasing the 50percent rock size and the thickness of the riprap blanket in areas ofexpected high boundary shear is recommended. Chart 703-1 can be used as a

703-1

guide for defining the location and extent of these areas in simple channelbends. The boundary shear ratios should be less than those shbwn in Chart703-1 for bends with smaller deflection angles or withbend radius to water-surface width (r/w).

(1)

(2)

(3)

(4)

(5)

(6)

59 References.

U. S. Army Engineer Waterways Experiment Station,of Rock Riprap, by F. B. Campbell. MiscellaneousVicksburg, Miss., February 1966.

larger ratios of

CE, Hydraulic DesignPaper No. 2-777,

U. S. Army Engineer, Office, Chief of Engineers, Stone Riprap Protec-tion for Channels, by S. B. Powell.

Ippen, A. T., and others, Stream Dynamics and Boundary Shear Distri-butions for Curved Trapezoidal Channels. Report No. 47, HydrodynamicsLaboratory, Department of Civil Engineering, Massachusetts Instituteof Technology, Cambridge, January 1962.

Ippen, A. T., and Drinker, P. A., “Boundary shear stress in trapezoi-dal channels.” ASCE, Hydraulics Division, Journal, vol 88, HY 5,paper 3273 (September 1962), pp 143-179.

U. S. Bureau of Reclamation, Progress Report No. l--Boundary ShearDistribution Around a Curve in a Laboratory Canal, by E. R. Zeigler.Hydraulics Branch Report No. HYD 526, 26 June 1964.

Yen, Ben-Chic, Characteristics of Subcritical Flow in a MeanderingChannel. Institute of Hydraulic Research, University of Iowa, IowaCity, 1965.

—-

703-1

NO

TE

:S

HE

AR

CO

ND

ITIO

NS

SH

OW

NW

ER

E

OB

TA

INE

DIN

TE

ST

SW

ITH

FR

OU

DE

NU

MB

ER

OF

0.34

.

WA

TE

RS

UR

FA

CE

t

26.

05”

W=

24”

+

CH

AN

NE

LC

RO

SS

SE

CT

ION

m7<

%<

2.07

TR

AP

EZ

OID

AL

CH

AN

NE

L

m2.

07<

7..2

.87

60-D

EG

BE

ND

To

=L

OC

AL

BO

UN

DA

RY

SH

EA

RS

TR

ES

S

~=

AV

ER

AG

EB

OU

ND

AR

YS

HE

AR

ST

RE

SS

INA

PP

RO

AC

HF

LO

W.

BO

UN

DA

RY

SH

EA

RD

IST

RIB

UT

ION

HY

DR

AU

LIC

DE

SIG

NC

HA

RT

703-

1

WE

S1-

68p

RE

PA

RE

DB

Yu

.s.

AR

MY

EN

GIN

EE

RW

AT

ER

WA

YS

EX

PE

RIM

EN

TS

TA

TIO

N.

VIC

KS

BU

RG

MIS

SIS

SIP

PI


SHEET 704

ICE THRUST ON HYDRAULIC STRUCTURES

1. The expansion of an ice sheet as the result of a rise in air tem-perature can develop large thrusts against adjacent structures. The magni-tude of this thrust is dependent upon the thickness of the ice sheet, therate of air temperature rise, the amount of lateral restraint, and the ex-tent of direct penet ation of solar energy.

1!Ice pressures from 3350to

30,0 0 lb per lin ft 1, have been used for design purposes. EM 1110-2-?2200 s) suggests a unit pressure of not more than 5000 lb per sq ft of con-

tact area and indicates that ice thickness in the United States will notnormally exceed 2 ft.

2. Although the work of Rose (2J stimulated number of studies on

ice pressure, the graphs proposed by him are of value for design purposes.These graphs are reproduced in HDC 704.

3. The ice thrust curves in HDC 704 are for ice thicknesses up to4 ft and hourly air temperature rises of 5, 10s and 15°F. Separate curvesare presented to show the effects of lateral restraint and solar radiation.The expected ice thicknesses, air temperature rise, and possible snowblanket thickness are dependent upon geographical location and elevationabove sea level. In the region of chinook winds rapid air temperaturerises can occur. The U. S. Weather Bureau has recorded a 49°Frise in twominutes at Spearfish, S. Dak. When the ice sheet is confined by steepbanks close to the structure, spillway piers, or other ver-tical restric-tions, the criteria for complete lateral restraint should be used. Thedirect effects of solar energy on the thrust are eliminated when the icesheet is insulated by a blanket of snow only a few inches thick.

(1)

(2)

(3)

4. References.

American Society of Civil Engineers, “Ice pressure against dams: Asymposium.” Transactions, American Society of Civil Engineers,VO1 119 (1954),Pp 1-42.

Rose, E., “Thrust exerted by expanding ice sheet.” Transac-tions,American Society of Civil Engineers, VO1 112 (1947), Pp 871-900.

U. S. Army, Office, Chief of Engineers, Engineering and Design, GravityDam Design. EM 1110-2-2200, 25 September 1958.

704

\

‘L

I NO LATERAL ] I II RESTRAINT I I I

16

1’ .

c—8 /

auL

mni?g ‘4

1-m>u11-

20

16

1’

8

4

0

0 I 2 3 4

ICE THICKNESS IN FEET

NO LATERAL

RESTRAINT

c,

COMPLETE LATERALRESTRAINT

16/

Cy

1’ ~

8

4

00 I 2 3 4

ICE THICKNESS IN FEET

SOLAR ENERGY NEGLECTED

24

20

18

1’

8

4

0

COMPLETE LATERAL

RESTRAINT

c\

A

o I 2 3 4 0 I 2 3 4

ICE THICKNESS IN FEET ICE THICKNESS IN FEET

SOLAR ENERGY CONSIDERED

LEGEND NOTE: CURVES BY ROSE,TRANSACTIONS ASCE>— >VOL 112,1947.

A- AIR TEMPERATURE RISE OF 5°FPER HOUR

B- AIR TEMPERATURE RISE OF 10°FPER HOUR

C -AIR TEMPERATURE RISE OF 15°FPER HOUR

ICE THRUSTS ONHYDRAULIC STRUCTURES

HYDRAULIC DESIGN CHART 704

PREPARED BY U S ARMY ENGINEER WATERWAYS ExPERIMENT STATION VICKSBURG, MISSISSIPPI WES 10-61

-


SHEET 711

LOW-MONOLITH DIVERSION

DISCHARGE COEFFICIENTS

1. Purpose. Several monoliths of the spillway section of a concretegravity dam are occasionally left at a low elevation during spillway con-struction for diversion of floodflows. Information on the discharge char-acteristics of these monoliths is necessary for determining the number ofmonoliths required to allow floodflows to pass safely. HDC 711 shouldserve as a guide for selection of discharge coefficients for this purpose.

2. Free Overflow. The flow over low concrete monoliths is gener-ally treated as flow over a broad-crested weir. The equation for freedischarge is:

Q=Cf(L-2KH)H3/2

where Cf is an empirical coefficient, L is the length of opening trans-verse to the flow, H is the head on the weir, and K is an end contrac-tion coefficient. The value of K is conventionally taken to be 0.10 forsquare-end contractions. The free-flow coefficient Cf varies with theratio of head H to width B of the broad-crested weir in the directionof flow. HDC 711a shows the variation of Cf with H/B resulting from

2 has recently shown theinvestigations summarized by Tracy.l Kindsvatereffect of boundary layer development on broad-crested-weir discharge. Therate of development is a function of the bottom roughness. However, pres-ent knowledge of this effect does not justify considering boundary layerdevelopment for diversion flow computations. The curve resulting from theclassical experiments of Bazin3 as shown by the solid curve in HDC Ylla isrecommended for general design purposes.

3. Submergence Effect. Discharge coefficients for broad-crestedweirs are not usually affected until the depth of submergence is about 0.67or more of the head on the weir. The phenomenon is commonly expressed interms of the ratio of the coefficient of the submerged weir to that of theunsubmerged weir %/cf as a function of the ratio of the tailwater depthon the weir to the head on the weir

H2/Hl “ Available data indicate thatsharp-crested-weir coefficients are more sensitive to submergence thanbroad-crested-weir coefficients.

4. Available data on the effects of submergence on discharge coef-2 495Y6 are summarized inficients for both sharp- and broad-crested weirs ~

HDC 7’llb. As far as is known, rectangular broad-crested weirs have notbeen subjected to submergence tests. A suggested design curve for sub-merged low monoliths is given in the chart.

711

5. Application. The suggested design curves given in HDC 711 should

serve as guides for estimating diversion flows over low monoliths. Incases where the head-discharge relation may be critical, a more exact rela-tion should be obtained by hydraulic model investigation. A model study of’proposed low-monolith diversion schemes for Allatoona Dam7 was made becauseof critical diversion requirements.

6. References.

(1)

(2)

(3)

(4)

(5)

(6)

(7)

Tracy, H. J., Discharge Characteristics of Broad-Crested Weirs.U. S. Geological Survey Circular 397, 1957.

Kindsvater, C. E., Discharge Characteristics of Embankment-ShapedWeir; Studies of Flow of Water Over Weirs and Dams. U. S. GeologicalSurvey Water-supply paper 1617-A, 1964.

Bazin, M. H., “Experiences n?uvelles sur l’ecoulement en diversoir.”Annales des Ponts et Chaussees, VOI 7, Series 7, 1896.

U. S. Geological Survey, Weir Experiments, Coefficients, and Formulas,by R. E. Horton. Water-supply paper No. 200, 1907’,p 146.

King, H. W., Handbook of Hydraulics for the Solution of HydraulicProblems, revised by E. F. Brater, lth ed. McGraw-Hill Book Co.,Inc. , New York, N. Y., 1954,Pp 4-18.

King, H. W., Handbook of Hydraulics for the Solution of HydraulicProblems, Xd ed. McGraw-Hill Book Co., Inc., New York, N. Y., 1939,P 99*

U. S. Army Engineer Waterways Experiment Station, GE, Sluices andDiversion Scheme for Allatoona Dam, Etowah River, Georgia; ModelInvestigation. Technical Memorandum No. 214-2, Vicksburg, Miss.,November 1948.

711

I

3.6

3.4

3.2

3.0

C$

2.6

2.6

2.4

-SUGGESTED DESIGN CURVE- .(BAZIN.)

1=:

‘USGS TESTS AT CORNELL

PRENTICE>

wDEERltVGSFIEL DAND BARKER

— -.

0.0 0.2 0.4 0.6 0.8 I .0 1.2 1.4 1.6 1.8 2.0

H,

B

a. FREE FLOW

I .0

0.9

0.8

0.7

0.6

0.5

0.4

_ _BASED ON K/NL9SVATER Z (EMBANKMENTS)

\ h\ % -

\

CORNELL TESTS ~ ~●

(ROUND. CR&T)< %%. \ ,

\<

/ -ssBRA TER’S 5 CURVE FOR

MA VfS AND V/LL EMONTE DA 7A v .>(SHARP CREST]

N’,\

\

f

\ v

0.0 0. I 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 I .0

H>

HI

b. SUBMERGED FLOW

NOTE : CF = FREE-FLOW COEFFICIENT

C~ = SUBMERGED-FLOW COEFFICIENT

NEGLIGIBLE VELOCITY OF APPROACH

RAISED NuMBERS ON SUBMERGED FLOWCHART ARE REFERENCE NUMBERS FROMTEXT.

LOW-MONOLITH DIVERSION

DISCHARGE COEFFICIENTS

HYDRAULIC DESIGN CHART 71 I

PREPARED BY U S ARMY ENGINEER WATERWAYS EXPERIMENT STATION, VICKSBURG, MISSISSIPPIwES 1-66

.


SHEET 712-1

STONE STABILITY

VELOCITY VS STONE DIAMETER

1. Purpose. ~draulic Design Chart 712-1 can be used as a guidefor the selection of rock sizes for riprap for channel bottom and sideslopes downstream from stilling basins and for rock sizes for river clo-sures. Recommended stone gradation for stilling basin riprap is givenin paragraph 6.

2. Background. In 1885Wilfred Airy 1 showed that the capacity of astream to move material along its bed by sliding is a function of the sixth

1 Henr Law applied this concept to thepower of the velocity of the water.overturning of a cube,2 and in 1896Hooker5 illustrated its application tospheres. In 1932 and 1936 Isbash published c~efficients for the stabilityof rounded stones dropped in flowing water.s~ The design curves given inChart 712-1 have been computed using Airy’s law and the experimental coef-ficients for rounded stones published by Isbash.

39 Theory. According to Isbash the basic equation for the movementof stone in flowing water can be written as:

[( )11/2

Ys - Yw 12v=c2gy (D) / (1)

w

where

v= velocity, fps

c= a coefficient2

g = acceleration of gravity, ft/sec

7s = specific weight of stone, lb/ft3

Yw = specific weight of water, lb/ft3

D= stone diameter, ft

The diameter of a spherical stone in terms of its weight W is

6W 1/3

()D=r

s(2)

Substituting for D in equation 1 results in

712-1Revised 9-70

~~hich describes Airy’. law .tated in paragraph 2.

4. Experimental Results. Experimental data on stone movement inflowing water from the early (1786) w rk of DuBuat5 to the more recentBonneville Hydraulic Laboratory tests8 have been shown to confirm Airy’slaw and Isbash’s stability coefficients. 7 The published experimental data

are generally defined in terms of bottom velocities. However, some are interms of average flow velocities and some are not specified. The Isbashcoefficients are from tests with essentially no boundary layer developmentand the average flow velocities are representative of the velocity againststone. When the stone movement resulted by sliding, a coefficient of 0.86was obtained. When movement was effected by rolling or overtwning, a Co-

efficient of 1.20 resulted. Extensive U. S. Army Engineer Waterways Ex-periment Station laboratory testing for the design of riprap below still-ing basins indicates that the coefficient of 0.86 should be used with theaverage flow velocity over the end sill for sizing stilling basin riprapbecause of the excessively high turbulence level in the flow. For impact-

8 has adopted a riprap de-type stilling basins, the Bureau of Reclamationsign curve based on field and laboratory experience and on a study byMavis and Laushey.9 The Bureau curve specifies rock weighing 165 lb/ft3and is very close to the Isbash curve for similar rock using a stabilitycoefficient of 0.86.

5. Application. The curves given in Chart 7’12-1are applicableto specific stone weights of 135 to 205 lb/ft3. The U.e of the average

(3)

—

flow velocity is desirable for conservative design. The solid-line curvesare recommended for stilling basin riprap design and other high-level tur-bulence conditions. The dashed line curves are recommended for river clo-sures and similar low-level turbulence conditions. Riprap bank and bedprotection in natural and artificial flood-control channels should be de-signed in accordance with reference 10.

6. Stilling Basin Riprap.

a. Size. The W50 stone weight and the D50 stone diameter—for establishing riprap size for stilling basins can be ob-tained using Chart 712-1 in the manner indicated by theheavy arrows thereon. The effect of specific weight of therock on the required size is indicated by the verticalspread of the solid line curves.

b. Gradation. The following size criteria should serve as—guidelines for stilling basin riprap gradation.

(1) The lower limit ofW50 stone should not be less thanthe weight of stone determined using the appropriate“Stilling Basins” curve in Chart 712-1.

712-1Revised 9-70 .

c.—

d.—

(2) The upper limit ofW50 stone should not exceed the

weight that can be obtained economically from the quarryor the size that will satisfy layer thickness require-ments as specified in paragraph 6c.

(3) The lower limit ofWIOO stone should notbe less thantwo times the lower limit of W50 stone.

(4) The upper limit ofWIOO stone should not be more thanfive times the lower limit of W50 stone, nor exceed thesize that can be obtained economically from the quarry,nor exceed the size that will satisfy layer thicknessrequirements as specified in paragraph 6c.

(5) The lower limit ofW15 stone should not be less than one-sixteenth the upper limit of W1OO stone.

(6) The upper limit of W15 stone should be less than the up-per limit of W50 stone as required to satisfy criteriafor graded stone filters specified in EM 1110-2-1901.

(7) The bulk volume of stone lighter than the w15 stoneshould not exceed the volume of voids in the revetmentwithout this lighter stone.

(8) WO toW2 stone maybe used instead ofW15 stone in cri-

7teria (5 , (6), and (7) if desirable to better utilizeavailable stone sizes.

Thickness. The thickness of the riprap protection should be

2D50 max or 1.5D1o()u , whichever results in the greaterthickness.

Extent. Riprap protection should extend downstream to where

nonerosive channel velocities are established and should beplaced sufficiently high on the adjacent bank to provide pro-tection from wave wash during maximum discharge. The re-quired riprap thickness is determined by substituting valuesfor these relations in equation 2.

7. References.

(1) Shelford, W., “On rivers flowing into tideless seas, illustrated bythe river Tiber.” Proceedings, Institute of Civil Engineers, VO1 82(1885).

(2) Hooker, E. H., “The suspension of solids in flowing water.” Trans-actions, American Society of Civil Engineers, vol 36 (1896),pp 239-

340.

(3) Isbash, S. V.,--/-

‘/v/

.-1.

Construction of Dams by Dumping Stones in Flowing

712-1Revised 9-70

,.

I

(4)

(5)

(6)

(7)

(8)

(9)

(lo)

Water, Leningrad, 19~2. Translated by A. Dorijikov, U. S. Army En-gineer District, Eastport, CE, Maine, 1935.

“Construction of dams by depositing rock in runningwater.” T~ansactions, Second Congress on Large Dams, VO1 5 (1936),Pp 123-136.

DuBuat, P. L. G., Traite d’Hydraulique. paris, France, 1786.

U. S. Army EngineerCofferdam Closure.1956.

U. S. Army Engineeron Submerged Rocks.April 1958.

District, Portland, CE, McNary Dam - Second StepLaboratory Report No. 51-1,Bonneville Hydraulic

Waterways ExperimentMiscellaneous Paper

Station, CE, Velocity ForcesNo. 2-265, Vicksburg, Miss.,

U. S. Bureau of Reclamation, Stilling Basin Performance; An Aid inDetermining Rinran Sizes, bv A. J. Peterka. Hvdraulic LaboratoryReport No. HYD-409, Denver,”Colo. , 1956.

“ “

Mavis, F. T. and Laushey, L. M., “A reappraisal of the beginning ofbed movement - competent velocity.” Second Meeting, International

>. .’-- /Association for Hydraulic Structure Research. Stockholm. Sweden.

1948. See also Civil Engineering, vol 19 (January 1949), PP 3~~ 39>and 72.

U. S. Army, Office, Chief of Engineers, Engineering and Design;Hvdraulic Desire of Flood Control Channels. EM 1110-2-1601.Wash-

“

ington, D. C.,‘1 July 1970./

7’12-1Revised 9-70

. .

(

IA.1

z o 1- ul 3?’

1000

800

600

400

-.

wII

/-!

?“(/

’4,’

~/

f//~

-A/

//

390

,,

1.

,I

i,

I1

AI

IIll

I4

IV[

//1

1I

I/

I/

*I

Ivf

Ii

1//

If

r

200

i/

#lII

/I

III

II

II

II

II

1I

II

I1

I1

II

II

II

1

tiiiii

t-t

-

II1

-If

/1/1

II

II

I11

1111

II

1/1

/1f’

II

II

II

II

I}

111/

Iv

III

IIn

f.

.1

fjIll

AII

A/“

__

__

__

__

J/,

,,,,

II

III

II

iI

I1

II

II

1I

II

I1

II

I

t~

//1/

1//1

/’II

I14

5&

l13

5

flf

.1

II

II

1I

II

II

II

1I

I1

I/

,,1

III

1[

II

I9

III

11

II

II

II

1I

I[

I1

II

IY

[11/

1/I

Iv

II

II

1r

1I

11

11

11

11

11

r1

r1

,r

,

+t

tt-

t+

1I

[I

Ii

I00

80 60 40 30 20 10-5

67

89

1014

1822

[0.4

0.5

0.6

0.7

0.6

0.9

1.0

1.2

1.6

2.0

2.4

AV

ER

AG

EV

EL

OC

ITY

,F

PS

SP

HE

RIC

AL

DIA

ME

TE

RD

50,

FT

BA

SIC

EQ

UA

TIO

NS

WH

ER

E:

V=

VE

LO

CIT

Y,

FP

S7s

=S

PE

CIF

ICS

TO

NE

WE

IGH

T,

LB

/FT

3

vs+

?,(

~s;’

)]’’2

(D50

)”2

7W=

SP

EC

IFIC

WE

IGH

TO

FW

AT

ER

,62

.5L

B/F

T3

W50

=W

EIG

HT

OF

ST

ON

E,

SU

BS

CR

IPT

DE

NO

TE

SS

TO

NE

ST

AB

ILIT

YP

ER

CE

NT

OF

TO

TA

LW

EIG

HT

OF

MA

TE

RIA

L

()

CO

NT

AIN

ING

ST

ON

EO

FL

ES

SW

EIG

HT

.V

EL

OC

ITY

VS

ST

ON

ED

IAM

ET

ER

6W50

1’3

D50

=~

D5C

I=

SP

HE

RIC

AL

DIA

ME

TE

RO

FS

TO

NE

HA

VIN

GT

HE

SA

ME

WE

IGH

TA

SW

50c

=IS

BA

SH

CO

NS

TA

NT

(0.6

6F

OR

HIG

HH

YD

RA

UL

ICD

ES

IGN

CH

AR

T71

2-I

TU

RB

UL

EN

CE

LE

VE

LF

LO

WA

ND

1.20

(SH

EE

T1

OF

2)F

OR

LO

WT

UR

BU

LE

NC

EL

EV

EL

FL

OW

)

=A

CC

EL

ER

AT

ION

OF

GR

AV

ITY

,F

T/S

EC

2R

EV

8-58

,9-

70W

ES

8-57

9

100,

000

80,0

00

60,0

00

40,0

00

30,0

00

20,0

00

10,0

00

8,00

0

6,00

0

4,00

0

3,00

0

2,00

0

EIt

1I

11

Ib

,

I1

II

III

IlfVi

ii#

1E

,r

EI

II

IIE

rw

I1

I!

11

1m

11

11

#1

11

I

.’1.“

11

11

11

11

11

11

11

i1

1{

11

11

11

I1

1)

I1

11

I/1#

[~~

III

II

I11

IL

IM5M

I

o12

1416

BA

SIC

EQ

UA

TIO

NS

v=C

~g(7

’;:)

]’’2

(D50

)”2

()

6W50

1’3

D50

=~

II

II

II

II

II

II

II

1I

I

1820

3040

48!2

.03.

04.

05.

06.

07.

08.

09.

010

.0

AV

ER

AG

EV

EL

OC

ITY

,F

PS

SP

HE

RIC

AL

DIA

ME

TE

RD

50,

FT

WH

ER

E:

V=

VE

LO

CIT

Y,

FP

S7.

s=

SP

EC

IFIC

ST

ON

EW

EIG

HT

,L

B/F

T3

7W=

SP

EC

IFIC

WE

IGH

TO

FW

AT

ER

,62

.5L

B/F

T3

W50

=W

EIG

HT

OF

ST

ON

E.

SU

BS

CR

IPT

DE

NO

TE

SS

TO

NE

ST

AB

ILIT

YP

ER

CE

NT

OF

TO

TA

LW

EIG

HT

OF

MA

TE

RIA

LC

ON

TA

ININ

GS

TO

NE

OF

LE

SS

WE

IGH

T.

VE

LO

CIT

YV

SS

TO

NE

DIA

ME

TE

RD

<n=

SP

HE

RIC

AL

DIA

ME

TE

RO

FS

TO

NE

HA

VIN

G..

TH

ES

AM

EW

EIG

HT

AS

W50

c=

ISB

AS

HC

ON

ST

AN

T(0

.86

FO

RH

IGH

TU

RB

UL

EN

CE

LE

VE

LF

LO

WA

ND

1.20

FO

RL

OW

TU

RB

UL

EN

CE

LE

VE

LF

LO

W)

9=

AC

CE

LE

RA

TIO

NO

FG

RA

VIT

Y,

FT

/SE

C2

HY

DR

AU

LIC

DE

SIG

NC

HA

RT

712-

I

(SH

EE

T2

OF

2)

RE

V8-

58,

9-70

WE

S6-

57


1. Purpose.and gullies. Underflow is required to

SHEETS 722-1 TO 722-3

STORM DRAIN OUTLETS

FIXED ENERGY DISSIPATORS

Storm drains frequently terminate in unstable channelsthese conditions dissipation of the energy of the out-prevent serious erosion and potential undermining and

subsequent failure of the storm drains. Adequ~t~ energy dissipation canbe accomplished by extensive riprap protection ~ or by construction ofspecially designed fixed energy dissipators. 3,4,5,6

2. Hydraulic Design Charts (HDC’S) 722-1 to -3 present designcriteria for three types of laboratory tested energy dissipators.3 Eachtype has its advantages and limitations. Selection of the optimum type

and size is dependent upon local tailwater conditions, maximum expecteddischarge, and economic considerations.

3* Stilling Wells. The stilling well energy dissipator shown inHDC 722-1 was Qeveloped at the U. S. Army Engineer Waterways ExperimentStation (WES).~ Energy dissipation in this stilling well is relativelyindependent of tailwater and is accomplished by flow expansion in thewell, by impact of the fluid on the base and wall of the well, and bythe change in momentum resulting from redirection of the flow to verti-cally upward. WES laboratory tests3 indicated that the structure performssatisfactorily for flow-pipe diameter ratios (Q@~*5) up to 10 with awell-pipe diameter ratio of 5.

4. HDC 722-1 shows the relation between storm drain diameter, welldiameter, and discharge. Designing for operation beyond the limits shownin HIIC722-1 is not recommended. Intermediate ratios of stilling well-&rain pipe diameters within the limits shown in HDC 722-1 can be computedusing the equation given in this chart.

5* lnpact Energy Dissipators. The U. S. Bureau of Reclama-tion (USBR)> has developed an impact energy dissipator which is an ef-fective stilling device even with deficient tailwater. The dimensionsof this energy dissipator in terms of its width are shown in HDC 722-2.Energy dissipation in the basin is accomplished by the impact of theentering jet on the vertically hanging baffle and by the eddies thatare formed following impact on the baffle.

6. HDC 722-2 shows the relation between storm drain diameters,basin width, and discharge. WES laboratory tests3 showed that thisstructure properly designed perfomns satisfactorily for Q/b~”5 ratiosup to 21. Intermediate ratios of basin widths within the limits shownin HDC 722-2 can be computed using the equation given in this chart.Design for operation beyond these limits is not recommended. The WES

—7’22-1 to 722-3

tests also showed that optimum energy dissipation for the design flowoccurs with the tailwater midway up the hanging baffle. Excessive tail-

water should be avoided as this causes flow over the top of the baffle.

79 Hydraulic Jump Energy Dissipators. The St. Anthony FallsHydraulic Laboratory (SAFHL)~ has developed the hydraulic jump energydissipator shown in HDC 722-3. Design equations for dimensionalizingthe structure in terms of the square of the Froude number of the flowentering the dissipator are also given in the chart. WES laboratorytests3 showed that this type of stilling basin performs satisfactorily

2*5 Up to 9.5 with a basin width three times thefor ratios of Q/b.storm drain diameter. WES tests were limited to basin widths of 1, 2,and 3 times the drain diameter with drops (drain invert to stilling basin)of 0.5 and 2 times the drain diameter. Parallel stilling basin wallswere used for basin width-drain diameter ratios of 1 and 2. The tran-sition wall flare was continued through the basin for W = 3D0 . Parallelbasin sidewalls are generally recommended for best performance. Tran-sition sidewall flare (l:D’) during the WES tests was fixed at 1 on 8.

The invert transition to the stilling basin should conform to the geom-etry of the trajectory of a flow not less than 1.25 times the drainoutlet portal design velocity.

8. HDC 722-3 shows the relation between storm drain diameter anddischarge for stilling basin widths up to 3 times the drain diameterwhich results in satisfactory performance. WES tests have been re-stricted to the limits shown in HDC 722-3, and the equation given in thechart can be used to compute intermediate basin width-drain diameterratios within those limits. General WES model tests of outlet worksindicate that this equation also applies to ratios greater than themaximum shown in the chart. However, outlet portal velocities exceeding60 fps are not recommended for designs containing chute blocks. Thischart does not reflect the outlet invert transition effects on basinperformance. The design of the basin itself (HDC 722-3) is dependentupon the depth and velocity of the flow as it enters the basin. Thevalues should be computed taking into account the drain outlet transi-tion geometry.

9= Riprap Protection. Riprap protection in the immediate vicinityof the energy dissipator is recommended. Preliminary, unpublished WEStest results3 on riprap protection below energy dissipators indicatesthe following average diameter (D<n) stone size should result in ade-quate erosion protection.

/-

V3()‘50=D~

where

D50 = the minimum average size of stone,weight of the graded mixture is larger

ft, whereby 50than D50 size

percent by

-

722-1to 722-3

D=v=g.

10.

depth of flow in outlet channel, ftaverage velocity in outlet channel, ftgravitational acceleration, ft/sec2

References.

(1) U. S. Army Engineer Waterways Experiment Station, CE, Erosion andRiprap Requir&nents at Culvert and Storm-Drain &tlets; HydraulicLaborato ry Model Investigation, by J. P. Bohan. Research ReportH-70-2, Vicksburg, Miss., January 1970.

(2) Practical Guidance for Estimating and ControllingErosion at7Culvert Outlets, by B. P. Fletcher and J. L. Grace,Miscellaneous Paper H-72-5, Vicksburg, Miss., May 1972.

Jr.

(3) , Evaluation of Three Energy Dissipators for Storm-DrainOutlets; Hydraulic Laboratory Investigation, by J. L. Grace, Jr.,and G. A. Pickering. Research Report H-71-1, Vicksburg, Miss.,April 1971.

(4) , Impact-Typ e Energy Dissipator for Storm-Drainage Out-falls Stilling Well Design; Hydraulic Model Investigation, byJ. L. Grace, Jr. Technical Report No. 2-620, Vicksburg, Miss.,March 1963.

(5) Beichley, G. L., progress Report No. XIII -Research Study onStilling Basins, Energy Dissipators and Associated Appurtenances -Section 14, Modification of Section 6 (Stilling Basin for Pipe orOpen Channel Outlets - Basin VI. Report No HYD-572, ~draulicsBranch, Division of Research, U. S. Bureau of Reclamation, Denver,Colo. , June 1969.

(6) Blaisdell, F. W., The SAF Stilling Basin. Agricultural HandbookNo. 156, Agricultural Research Service and St. ArAhony FallsLaboratory, University of Minnesota, Minneapolis, Minn., April 1959.

722-1 to 722-3

,x

L

1-lL

.

noKw1-

z

20

10 /-.

5

/2 - I / // //// /y‘ I1

I

II IUNSATISFACTORY

II‘1 2 5 10 20 50 100 200 500 I 000

DISCHARGE Q, CFS

BASIC EQUATION

Dw

()

Q&

=0.53 & —Do”

‘OR 2.5 ’10Do

WHERE:

DW = STILLING WELL DIAMETER, FT

DO = DRAIN DIAMETER, FT

Q = DESIGN DISCHARGE, CFS

0.6 -

0.4

/

0.2 /

/

o0 0.2 0.4 0.6 0.8 1.0

SLOPE, VERTICAL/HORIZONTAL

CHANNELINVERT>

VERT

ffOR

7-

MELEVATION

STORM DRAIN OUTLETSENERGY DISSIPATORS

STILLING WELL

HYDRAULIC DESIGN CHART 722-1

WES 7-73

I

➤ 20[I I I I I 1 I .\ A

IA.

0°I I I I I I

u 101\\

@JyfllD’~,Ll

u) ,[

I 2 5 10 20 50 100 200 500 1000

DISCHARGE Q, CFS

BASIC EQUATION

w ()= 1.3 *Q

—s21x

FORD02”5 C.&”s

WHERE:

w = BASIN WIDTH, FTDo= DRAIN DIAMETER, FT

Q = DESIGN DISCHARGE, CFSVI = PIPE VELOCITY, FPS

t-l

PLAN

BEDDhVG L

SECTION

STILLING BASIN DESIGN

H=:(W) c+(w)

L=:(W) d=&(W)

a=+(w) e =;(W) STORM DRAIN O JTLETSENERGY DISSIPATORS

IMPACT BASIN


WES 7-73

‘._

‘lo 20 50 100 200 500 1000 2000 5000 I 0,000

DISCHARGE Q,CFS

BASIC EQUATION

w ()— =0.3 ‘+ Q 59.5Do

FOR —Do2”s

WHERE:W = END SILL LENGTH, FT

4DO = DRAIN DIAMETER, FT

Q = DESIGN DISCHARGE, CFS

RECTANGULARSTILLING BASIN

HALF-PLAN I A

DESIGN EQUATIONS

“:

F ‘~

TRAPEZOIDALKm

&.._-STILLING BASIN f

HALF-PLAN

SIDEWALL tr

i

FLOOR BLOCKS

CENTER-LINE SECTION

(1)

4= %-’+-) (2)F =3 T030 d;=(l.10-F/120)d2 (3CI)

F =30T0 120 d;=0.85d2 (3b)

F =120 T0300 d:= (1.00-F/800) d, (3C)

4.5d2 STORM DRAIN OUTLETSL~=— (4)F0.38 ENERGY DISSIPATORSz=+ (5) STILLING BASINC =0.07dz (6)


WE9 7-73


SHEET 722-4 TO 722-7

STORM DRAIN OUTLETS

RIPRAP ENERGY DISSIPATORS

1. Purpose. Criteria for the hydraulic design of fixed energydissipating structures for storm drain outlets are presented in Hydrau-lic Design Charts (HDC’S) 722-1 to 722-3. Under some conditions adequateenergy dissipation can be accomplished more economically using riprap asan alternate to fixed structures. HDC’S 722-4 to 722-5 present threebasic riprap energy dissipator designs developed at WES.1~2

2. Scour Holes. Scour holes at storm drain exit portals effec-tively dissipate flow energy and reduce downstream erosion. However,uncontrolled scour holes can undermine the storm drain with subsequentstructural failure. Basic laboratory tests were conducted at WES1 duringthe period 1963-1969 to investigate scour hole development and erosionprotection in cohesionless material downstream from storm drain exitportals. These tests showed that the length, width, depth, and volumeof the scour hole could be related in terms of the storm drain diameterDo in feet, the discharge Q in cfs, and the flow duration t inminutes. The tailwater depth TW in feet over the storm drain invertwas also found to be important. The following set of design equations2describes the basic scour hole dimensions for two controlling tailwaterconditions.

L

[)

Q0.71

sm

( )]

~o.125~ ‘c D2.5

o

Dsm

[) 1

— 0“37’ (t””’o)Q

~ ‘c D2.5o

(1)

(2)

(3)

(4)

722-1 to 722-7

where

L~m = scour hole length, ftDsm = depth of maximum scour, ftw = half the width of the hole at the location of maximum scour, ft;: = volume of material removed from scour hole, ft3

Empirically determined values of C in the equations above for the two

controlling tailwater conditions are:

TW Equation No.~

1 2 3 4—— —

>0.5 4.10 0.74 0.72 0.62

~o.5 2.40 0.80 1.00 0.73

3. HDC 722-4shows dimensionless scour hole profiles and crosssections for the two limiting tailwater conditions.

4. Horizontal Riprap Blanket. HDC 722-5 shows the recormnended

length Lsp and geometryrequired for satisfactoryflow from a storm drain.using HDC 722-7.)

of the horizontal. riprap blanket protectiondissipation of the energy of the design out-

(The required D50 riprap size can be estimated

5* Preformed Scour Holes. Laboratory studies have shown thatsatisfactory energy dissipation of storm drain outflow occurs in riprap-lined, preformed scour holes of nominal size. HDC 722-6 shows the rec-ommended design for preformed scour holes 0.5 and l.ODO deep. The D50minimum stone size required for each scour hole depth can be estimatedusing HDC 722-7.

5. Application. Study of the basic test data indicates that theresulting design criteria are generally applicable to both circular andrectangular conduits flowing full or partly full. For rectangular con-duits the conduit width is used in place of the diameter Do of thecircular conduits.

6. References.

(1) U. S. Army Engineer Waterways Experiment Station, CE, Erosion andRiprap Requirements at Culvert and Storm-Drain Outlets; HydraulicModel Investigation, by J. P. Bohan. Research Report H-70-2,

Vicksburg, Miss., January 1970.

(2) , Practical Guidance for Estimating and ControllingErosion at Culvert Outlets, by B. P. Fletcher and J. L. Grace, Jr.,

Miscellaneous Paper H-72-5, Vicksburg, Miss., May 1972.

722-1 to 722-7

‘.—

-—-

DS

DSM

FLOW= 1 ORIGINAL GROUND LINE

I I I IO I.OOO-FT-DIAMETER CULVERT

A ❑ 0.333 -FT-D[AMETER CULVERTAA 0.224 -FT-DIAMETER CULVERT

- CUTOFF fJ AWALL

1.21 I I I I I I I I I Io 0.1 0.2 0.3 0.6 0.7 0.8 0.9 1.0

_+!i4 L&

DIMENSIONLESS CENTER-LINE PROFILE

DO 7TWORIGINAL GROUND

o I A

0.4 ❑

\ u1

0.8 -’)“

1.2,0 08 060.4 0.2 0 0.2 0.4 0.6 0.8 LO

w~ /w~M

DIMENSIONLESS CROSS SECTION AT 0.4LsM

TW > 0.5D0

FLOW_ 1 ORIGINAL GROUND LINE

G .I

~ CUTOFF WALLflo

0.4

0.8~ oII A~

1.200. I 0.2 0.3 0.4 0.6 0.7 0.8 0.9 1.0

A Ls ?;~M

DIMENSIONLESS CENTER-LINE PROFILE

DO ORIGINAL GROUNDo-

0.4 aDs

DSM

0.8 \. A

1.21.0 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1.0

w*/ w~M

DIMENSIONLESS CROSS SECTION AT 0.4LsM

TW ~ 0.5D0

NOTE: Ls =DISTANCE FROM OUTLET TO Ds, FT

L s~ ❑ DISTANCE FROM OUTLET TO END OF SCOUR, FT

Ws =DISTANCE (R &L) FROM ~ TO DS AT 0.4Ls~, FT

Ws~=DISTANCE (R & L) FROM ~ TO O.0~ AT 0.4Ls~, FT

DO =DIAMETER OR WIDTH OF STORM DRAIN, FT

TW =TAILWATER DEPTH ABOVE DRAIN INVERT, FT

L lNE

LINE

STORM DRAIN OUTLETS

SCOUR HOLE GEOMETRYTW > 0.5D0 AND 5 0.5D0

0s ❑ DEPTH OF SCOUR, FT HYDRAULIC DESIGN CHART 722-4Ds~=MAXIMUM SCOUR DEPTH, FT WES 7–73

(

5( 4( 3(

LS

P

Do

2( 1( (

co00

00

000

00hp

()Q—.1.7

-Do

+8

Do5

~

o

0A

DE

QU

AT

EO

AL

MO

ST

AD

EQ

UA

TE

●IN

AD

EQ

UA

TE

000

00

}00

.---

--Iv

NO

TE

:D

o-

DIA

ME

TE

RO

RW

IDT

HO

FS

TO

RM

DR

AIN

,F

T

Q-

ST

OR

MD

RA

IND

ISC

HA

RG

E,

CF

S

Lsp

-H

OR

IZO

NT

AL

LE

NG

TH

OF

BL

AN

KE

T,

FT

PL

AN

EL

EV

AT

ION

NO

TE

:D

,.-

MIN

IMU

MA

VE

RA

GE

SIZ

EO

FS

TO

NE

,F

T

)

ST

OR

MD

RA

INO

UT

LE

TS

RIP

RA

PE

NE

RG

YD

ISS

IPA

TO

RS

HO

RIZ

ON

TA

LB

LA

NK

ET

LE

NG

TH

OF

ST

ON

EP

RO

TE

CT

ION

HY

DR

AU

LIC

DE

SIG

NC

HA

RT

722-

5

WE

S7-

73

.._

“L-

—

A

1-U-. Do 70N3

/

70N3

I ,

d. 70N3

70N3

A

PLAN

VARIES (0.5 -7.0 Do)

SECTION A–A

NOTE: Do = DIAMETER OR WIDTH OF

STORM DRAIN, FT

STORM DRAIN OUTLETSRIPRAP ENERGY DISSIPATORS

PREFORMED SCOUR HOLE GEOMETRY

HYDRAULIC DESIGN cHART 722-6

WES 7-73

I

—.

x

1.0” I I I I I I

0.5

0.2

0.1

0.05

0.02

0.01

8Iy

0.005 “ /

0.002 ‘ 1 1 I I I I

I I I I I I I

,//

/4

# / A/

/3

04‘

/

/

#’ “

/

I I I I_

c TYPE PROTECTION Io 0.0200 HORIZONTAL BLANKET❑ 0.0125 0.5 D0-DEEP PREFORMED

SCOUR HOLED 0.0082 I.ODO-DEEP PREFORMED

SCOUR HOLE 7

--L I I I 1 I I0.2 0.5 1.0 2 5 10 20 50 I00

Q

BASIC EQUATION

()

4/3D50 .C Do Q——~ TW D0512

WHERE:

D50= MINIMUM AVERAGE SIZE OF STONE, FT

Do = DIAMETER OR WIDTH OF STORM DRAIN, FT

Q = STORM DRAIN DISCHARGE, CFS

TW = TAlLWATER DEPTH ABOVE DRAIN INVERT, FT

STORM DRAIN OUTLETSRIPRAP ENERGY DISSIPATORS

D50 STONE SIZE


WES 7-73


-——SHEET 733-1

SURGE TANKS

THIN PLATE ORIFICES

HEAD LOSSES

1. Thin plate orifices are often used in surge tank risers to re-strict the flow during load-on and load-off operations. Computation of thehead losses through these orifices is of interest in the design of surgetanks.

2. A number of experiments have been made on head losses through or-ifices in straight pipe. When an orifice is placed in a surge tank riserclose to the penstock tee, the energy loss of flow entering or leaving theriser is affected by the orifice flow. Indri’s(2J extensive study of ori-fices in branches has made available new data on head loss coefficientsconsidered to be applicable to surge tank problems. The pipe used in thisstudy was 9 cm (3.54 in.) in diameter. The orifice plates were located inthe branches lzs mm (1.92 in.) from the center line of the main pipe. Thetest results indicate that the combined tee and orif”ce loss coefficientswere independent of Reynolds number for iRe>s)(10 .

3. HDC Tss-lpresents a head loss coefficient curve for thin plate~ orifices in tees. The head loss coefficient is based on the combined tee

and orifice head loss. Indri’s data shown in this chart indicate that asingle curve is applicable to load on-load off turbine conditions. Alsoshown in this chart are head loss coefficient curves by Weisbach(s) andMarchetti(l) for thin plate orifices in straight pipe. These curves indi-cate that the location of the orifice with respect to other disturbancesaffects the head loss.

1. The data in HDC 733-1 are based on the equation:

V2‘L

=K—0 2g

where

HL = head loss across the orifice or orifice andK. = head loss coefficientv= velocity in riser, ft per sec

The head loss coefficient is plotted as a function ofsquare of the riser diameter D to the square of theA sketch of an orifice in a straight pipe is includedposes of defining the terms involved.

tee, ft

the ratio of theorifice diameter d .in the chart for pur-

-———_— 733-1

5* References.

(1) Caric, D. M., “Tehnicka hydraulika.” Gradevenska,(1952).

Knjiga, Belgrad

(2) Indri, E., “Richerche sperimentali su modelli di strozzature per pozzipiezometrici (Experimental research on models of constrictions forsurge tanks).” L’Energia Elettrica, vol 34, No. 6 (June 1957), pp554-569. Translation by Jan C. Van Tienhoven, for U. S. Army EngineerWaterways Experiment Station, CE, Translation No. 60-3, Vicksburg,Miss., April 1960.

(3) Weisbach, J., Untersuchungen in den Gebieten der Mechanik undHydraulik. Leipzig, 1945.

.-

733-1

.3000

2000

LEGEND

● INDRI-DOWNWARD SWING

I 000 — O INDRI - UPWARD SWING

800

600 TMAR

400

300 -

200

100

80

60

40

30, [

20

/IVDRf -

10//

6 /1

/f

6 //

gl

4 .r

3/

2 ~

dI

I

EQUATION

WHERE:

HL=HEAD LOSS ACROSS ORIFICE, FT

KO=HEAD LOSS COEFFICIENT

V =VELOCITY IN PIPE, FT PER SEC

‘1 2 3 456

PREPARED ❑ Y ‘J S ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG, MISSISSIPPI

/

/, A/

//“

.//

fETTl - /~/

/

/

{

/

-WEISBA CH

DEFINITION SKETCH ITI

10 20 30

SURGE

40 50 60

TANKS

THIN PLATE ORIFICESHEAD LOSSES

HYDRAULIC DESIGN CHART 733- I

WES 10-61

hydraulic design criteria us army

Documents