FLOOD07353

• County: Statewide
• Basin: Statewide
• Title: Hydraulic Engineering volume 2
• Date: 1/1/1994
• Prepared By: American Society of Civil Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

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770

HYDRAULIC ENGINEERING '94

Table 2
drag eM
shape of val ns coefficient hLl/ch c.
close to 0,4- 0.50 81.92 0.013
ell1psold 85.33 0,014
ellipsoid 0,70 5.0 .0.044
close to 0,6 - 0,7 11,25 0,025
ellipsoid 16.20 0,030
16,5 0.025

It turned out that the spheric grains characterized of significant
stability in the flow bed ,however . when the reslstance
coefClclent increased the grain stability decreased and
consequently it was easler to move the grains fro. the botlo.
because of the less shear stresses. The critical stress curves for
spheric and elHpsold particles are shifted relatively each other
towards lower values and quantity f "" 0.02. Raudklvl's (19821
studies confirmed consecutive lowering of the critical stress
values which could be caused by protrusion of grains. If the ratio
of the protrusion part of grain to Us diameter 1s equal 0.5 the
nondlmenslonal critical stresses will be O.02.t~refore the effect
of the grain pf'()truslon 1n the multifr:a.ctlonal _terial will be
also decide of the critical stresses values.The $ffect of the gratn
protrusion can explaln the decrease of the noncUmttnsional stresses
values when the grain diueter dl increases.
The nondi_nsional stresses valult's calculatlt'd according to the
equation (:)).!t is easy to observe that the stress values decreases
\lith the increase of the dept in the flow bed or \lith the
decreasing diameter of grains. Independently on the incipient
IIOveaent studies the series lQeasurements aceo.pan1ed wi th 1991,4
(Table 1) were carried out. The alm of the measurements was to
define the II\8.SS of the transport IDaterh.1 in the wave of
freshet. The sUlple of 233 grains of the natural material traced
tantalum-182 was used in the composition presented 1n Table 3.

where: Sp = c/(a b)O.5 - shape coefficient

a - longest d1ameter.b - mean diameter-,e - shortest diameter

The spheric coeff1cient of the grains dependently on their
relative diameters is described by the following equation:

. III 0.91 (a/b}-a.es

After f'lood,applying the radiation detectors the longitudlna:
distribution of the traced grains was deteralned via ttlt
lIleasurement of a distance where the grains were transported fror
the injection place. The centers of gravity of each decoDlpostttar
(for each fraction and shape) were calculated according to: Cc"
L nl 111 L hi (Table 3).

where: n1 - number of grains of the fraction

-....

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FLUVIAL HYDRAULICS

771

LI - distance of their detection
lnjection cross sectlo accordlng f'ro. the
The freshet lasted :) hs the n
of "belt .. of the tl"'ans~rt Bt -:X;~lIJlI flow was 0=150 ..3/s. tM width
layer was E ... O. 1211. All the grainsl1l . the thickness of a transport
. 3S . according :frolll the InJe liel"e detected on the dlstaJ'lc L
(Tab. 3), that the grains o:f thect!on cross sectlon. It turned :ut
7.0_land the ellipsoid shapes :ean diameter d.= 0.05m (Cc ""
1.0_). On tbe other hand th transported easlest (Cc
were Iluch Illore dlf:ficuit 1: ~rains of' disks. plates. bars Shape:
anot.her. More accurate of the r&nsport because they wedeged
Incipient movement reqUIres o;f':etct of the araln shape on th:~;
Table 3 e ermlnatlon of the drAft ~
_ ~orce of'

fractIon number of graIns
(.) s,.-O. 7-0,86 Sp=0.6 Co (m)
0.02-0.04 Sp=0.5 Sp<O.4- Fraction
37 23
0.04-0.06 16 28 32 4,0
0.06-0.08 23 18 13
8 8 7,5
>0.08 4 7 5 4.7
7 3
I 2,0
Co (shape) 5.3
7,0 4.0 3.5
he grains. Howe

( ver, at the
the critical shear stressesP:~e~ stage of studies the values of'
trains conslderins: theIr size 8.hd s~~d on IIllscellaneous of the

ConclUSions

In lIOuntaln streaJIS the crtti
:e;~:l ::r:ns~~::~; the local C~~~e S~::~:~onsIn non-unitol". bed
T'~ , the &raIn size
I'le !lean grain fr. t!
....Iest. ac on and elllpsoidal
shapes are transported

~ferences

Oas-tnl k W 1993
" . , BegInning oC Bed Load
. aszyty Naukowe" AR Cr Hollon In MountaIn St
..Jlplu P. . Bed Load Transport ~ow Poland. No 171 (In POlish) I'"eB..llS.
Proc. 111 lSRs n Gravel Bed Streams.So
:ora{ U. H. 1981, Bed i.~' ug::~ MiSSISSiPPi. 1988,925"'9;:. Properties
Rlve1"S .Sedllllent tMUlSpo~g~ Equations for Steep Mountain
"lCr..~~\~~~9911::.453-490. n Crave I Bed Rivers.J. Wlley &
Invest! tt' ~ Load Transport in MOunt 1 Rl
"lchallk A :r on Zeszyty Naukowe" Aft can verso Radlotraeer
3-lb i~, lnlk 11,1988. BegInnIng oC ;;:0", No 138 (In polish)
kalldklllJ ern.S)'lll. on IUver Sedime Load Hotlon In Rivers
'J J.R..Elt... R,I882 5tabl11t ntfatlon NlsslsSlppl ,177-184 .
. of the 11..... . Y 0 ftrJDOQr 1
.~~raulics DIvisIon" BY9 I syers In rivers.
. 982 ,1047-1057,

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...,....