|
<br />
<br />,
<br />
<br />"',
<br />',fI,
<br />,
<br />
<br />,
<br />
<br />.
<br />!';
<br />
<br />.
<br />
<br />THRESHOlDS FOR GRAVEL AND COBBLE MOTION
<br />By KatherIne J. CI1ase'. A8socIa1o _. ASCE
<br />AB5TAACT: Flows....., ~....... mDIon of roc:IWon ....... bIr fIIong the Gunnlllon RIver In BIllICk c.n.
<br />01 the GunnIBQn NllIIo..... Monumenl ... ob8efVed. Grawll ~ cobbIeii .. ~ 8lld ~ In *
<br />~ n'ollflll8r8Ur1eC8 ..,.,.In1h8vtctn111l18 oIth8tc:ll:U..~__...
<br />......torm....Upalnlamdwn. OIthe110rvdm~mloW.43rno\'18. ThIee ..........
<br />1oC8lcultllle1h8ve1oc1y_0I.....~reauInM1tQmove8lllChrodl:. Theee veIodI8iIand......
<br />_....._0_............_ Tho~.;;"I';_....__._
<br />nwayof"'Rldls..tnrno1londurli1g"'_~1Ind tIoW8..-yto...._
<br />.-........................__. To___....."__
<br />profIBI, bed pocket MQI88. and turbUtenee frOm IBId ~ 8hQukI be 8lUcIBd fUrther.
<br />EXPERIMENT DESCRIPTION
<br />Wo moosurod end morIcod 145 gravels end cobIlIos In situ eIong the edge 010_ bo
<br />Painted rnck8 ranged from 2 em 10 15 em In dlamolor. We p/1otognIphod end_
<br />groups 01 rocIcs, end surveyed eech groop'alocallon.
<br />The BtnBU 01 Redamadon (BUREC) ~ttrBB8Bd low reIeBsea from the upslr88m CrystaIDrII
<br />lor ... 10 IwaIve hour period.. BUREC.- 17 m' 1-. then 22 m' 1-,29 m' l_
<br />end 45 m' IfIOO. The IIoW returned 10 10 m' 1_ (Iypk:eI beae IIoW at _limo) slIIr...
<br />.-.e. 45 m' lsec hall been equalled or _ ebouI3O% 0I1he lime since 1976.
<br />Durtng each 1IoW.-.e. we -..:I naN_lnlhevlclnltyol each rock_OIl
<br />morIcod weier surface _Ions. We were ClIIOIU not 10 d_1he rocks (not_m-.
<br />the .........,.. merked byftags) durlngveloclly ~ Allor each reIosse, 1I1t_
<br />_e again photogrephod end 8UlVOYod 10 dolecl_ MIsatng rocks wore noI_
<br />EXPERIMENTAL RESULTS
<br />0I1he 145 merked rocka. \II wore expoeed 10 Ihe current end 44 moved. _..
<br />moved lOnged from 210 II em In _or. Some 01 those rocks mey hove moved_aw
<br />onc:e. .,.. any 1n1llol moIIon wes 8IUdIod, As depIclod In FIgure I, noIhIng moved dIIIng h
<br />17 m' lsec releeae. 6 rocIcs moved during 1110 22 m' lsec ........1110 29 m' 1_1ow.-
<br />10 rocks. end the 45 m' lsee naN moved 28 rocIcs. Over half 011110 mobile rocka __
<br />then Ihe ...-roundIng bod material, e.g.IhelrDm/D50 _were U-Ihon 1.2 (1oilIortOo
<br />- Ihe rock's medium exIa length, end D50 . lhe _ _lor which 50% 0I1I1t pIltldo
<br />comprlalnglhe bod _ 810 _). ~6 0I1he dIspIecod rocks were ..-....h
<br />surrounding bod motorial ((DmjD501 <0,8). All but one 01 those 6 rocl<a moved dlllng ""..
<br />(45 m'/see).-.e.
<br />Atll1oboaelloW 0110 m' IfIOO.lI1ope1nled rnck8werenot expoeed 10 now. AlI7m"-
<br />tho rocIcs ~ mean _ up 10 0.3 m/sec end sheer _ up 10 15 NI'"
<br />The 22 m' lsee naN .-.e rllSUIed In _mum mean veIo<:1lIes 01 0.410 0.8 m/ll8C ool"
<br />1035N/m' sheer_ VeIoc1IIosend__durlngll1029m' 1---
<br />s1m1ar 10 1110 22 m' lsee.-.e. Durtng Ihe 45 m' lsee.-.e, _ --
<br />_010.810 1,3 m/seeend ob88rvod depIha end water _sl_radfng.'
<br />10 90 N/m'. Notothal orIy Ihe maxtmum _ end depIha were 1118lllIUrod. and_
<br />IOngos 01 er1llcal_ end shears wore determined. _ 01 d_ w1_
<br />Welor _ ~ ch8ngod very 1l1li0 88 dIach8rgos Increeaod. Tho upoIr8801-
<br />_ 8\ope wes I'l(, lor "'I rei...... _1110 downatleom _ _1Pcreuod""
<br />l.n 811he 10. 17 end 22 m' lsee IIoWa 10 Ul'l(, 811110 29 m' IIOC end 45 m' r"'''''
<br />
<br />. Protect EnginlMlr, Tagg.rt Ef9neering As8ocIlIl88, Inc., 2:5:ZO 18th Sbget, SUIeB 210, 0llnVIr. CO""
<br />
<br />790
<br />
<br />,,-
<br />
<br />...
<br />
<br />THRESHOLDS-GRAVEL & COBBLE
<br />
<br />.
<br />
<br />.~
<br />
<br />791
<br />
<br />Tho -- depth 01 weier _1110 bod was 0,6 In.
<br />
<br />ItIIIAL ROCK 1kM:1l[N1
<br />
<br /> ~
<br /> .
<br /> . Om/D50~I.2
<br />'.""IIOiIO "
<br />'0"1{ . O.8<(Ilm/Dsol< 1.1
<br />""'111/( ..
<br /> u
<br /> "
<br />
<br />11 m~l/sec
<br />
<br />
<br />22 rrt--J/Rr, 29 ,..3/_
<br />flOWI/oU[
<br />
<br />FIgure 1
<br />
<br />45".,..3/_
<br />
<br />PRfDlr.TIVE EOIJATIONS
<br />Unon_ _Ior/nclplent moIIon
<br />_01 lIIIlvol 8nd _In non~~'" wllh8mp/laalaonlnolplenl
<br />::., ~Y":1cIod 1ntIIoJ moIIon oIlI1oalOOy rocks~JTho - equedona
<br />..._ _r _. 8nd ~== J.D, Smith's p/lyaIc8ay~:d'=
<br />"" -Ip dovoIopod by Holey (1969) Is: oquelfon for - sheer.
<br />'. -'" ""'0[ .Jr -iM' "'01. (SM+D ~] '"
<br />LK(;'. III J. \u..f7ItJ.chmQJJ
<br />v....it~ot...low~ OftChePdcl881adl8t.m::e
<br />mM8u::r~~r:;'':';'-I=Uf>>d,Wh8reZ.Ihe~~~~<<tIaec).
<br />SM. rodl'.ahotI_/8nglf'! (ftJ 8U lothBbed,
<br />...-............"..(11)
<br />=.~.or1h&moI(smunlld9l8/lg1h
<br />.. _...;::'~(II), ~.:.~a)+..&llM',8)"....lo)
<br />IMOoodr'&,RlOmllnl:ann th9p '1:1nh..........._end1tlehortlo......
<br />c, ~:-a~"J18)".c:oa{e)-(Gl4)e1n(an
<br />~ .....,..'L. C' 1=-_)
<br />.... :.-:.;not~IoU=.':'-~~~.8hIpe 1Icb, SF, where SF. SMJ~ The C'.JSF
<br />.. IllDIIiwIlllQft af IJ" (ft/8ec.) ( Neas) . 2..
<br />
<br />~ ~ dortvod by Wiberg end SmIIh (19878) Is:
<br />CO ~.,~--.nM ]
<br />L ... II .)0 + "1./ Uln(.n
<br />'_' dn~.Qu,""" "-
<br />· 'k~ PGckfIl: llIr8rlQ.. tcr/{(apw. -spw)D..J
<br />~ .JO&l.Hl.~D /D!O."'11 (0.050 fn
<br />"_~.....O;;_...)..WIiCj;;.",,'::l~= --.. ::r.,_.........11987b>>
<br />CC_o dn......1IIIlAi It'agooetrlclenl ~ bed...............
<br />..~~C'.__~ldatlical8lt'ess
<br />O'a tor -.Cll8fIcIerw:"-Ide8cnbesQraln_
<br />IoN. v. IF' ,U88d(Alt*D..W. WhlqAxa.....Ifi8.-'
<br />.. Iowlllplh~~:,a..,n:;,,""1ls1n a=1.3 pa'1IcIe'1; cross8ldOlVII_~lothB
<br />',- "~lMfoflhebi"" Inpro1le"meauredUPtromlJebed
<br />I 'u'.>. ...~~8IIiI1lA9dbyZ..;,kJ30(m)
<br />~)....,~=_n
<br />~ ~ 0.407 (....mee ..!eatl._d1en 1000, f . qJz .~. K "1",* \ W'tlIW8 ...__
<br />'"'"Ill pIl)JJ8). ThltslUdyll88d ." lY"vun
<br />
|