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<br />ETL 1110-2-120
<br />Chanse 1
<br />26 MlIy . 19>71
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<br />1959 ealtion,'may be used to determine the local boundary
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<br />.~ict:.:;~, Inclosure 4 is a graphical aid for solution of'this ~~f;~~~',~~~~.i):
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<br />i{li::' ;';<~~;~t ,., {4)" Equaticm (32) is based on ilJe assumptions off~il;q~~~g~~~_t'
<br />,~. ''-'i'C.' flow conditions and nOTlDal logarithmic'vertical velocity distribution ,~'-~~i',",;:;~' },
<br />,:C ":'<':; -produced by 'lIIIiform channel fl~w. Fully TOUgh flow conditions. in.':~".
<br />. ',;,c'.11ri." ,;~/ the range indicated on Hydraulic Design. ChaTt '631. noTlll&Uy occur lnq .;
<br />, . ,:iir:V, channels which require ripra;p protection, .but significant deviations
<br />';;E~';F: .' ",jj;1bom the :normal logarithmic vertical velocity distributi-onoccur 11l,:;:~~
<br />'''"Wi d1annels which have non-lDliform cross sections, varying slopes and .
<br />". ,>.. :di-fferent bed andbanl TOUghness C0e-fficients . Thus, 1lIlless a lDIiform;~:,~~'..;'$.',
<br />\~\,;J', 'channel cross section with identical bed and banl ripTap 1IIaterial -occurs "''J.'''t'~ffi'
<br />':,'(:.'" , ,,: GI a constant slope .over a suffici.ent distance to pl'Oduce lDIiform>~::#' ".'
<br />~'<t'~"":"~~\fhannel,~ow at normal depth_an~ velocity, llIax~mum local bOlDldary'sheat:'
<br />~.i1,~:':.,: .'.:>!,.'. ':'Values Will be greater 'than~ndlcated byequa-uon (32), -due 1:0 grelrter,:". 'j
<br />'$':" ;:wt~:i1lcal~zed. veloci ties ~ l'r7"';ll"e-pulsations. As th: e~ectso~:!,\'ff:,~'.
<br />~...~..".;;,.i.f..,:..'.., ':...:~>,;cont~bUt1.~g f~cto~stodev1&tlons fz:om no:mal loganthmic VertlCa. .~". o.c,..:
<br />'-.:"g::..~".~,. ~.: -.'.".' velOCIty dlStrlbutlon have not been establ1shed, values of local. .',:,7." .' .' "',.,1;0,>
<br />';~re:.:- :1< 'bolDldary shear computed from .equ~tion (32) should be iucrea~ed by a :;t1';,:,:;,i;:.~~
<br />:'~';'i!f,'.q, "',;;;" :factor of 1..5, ,except when flow IS at or near normal depth ~n a channel;. :,~"".,:
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<br />'.1;,,_,y,:>.:',.~!;':'" wi'th uniform CTOSS sectiOn 1IIIdequal bed and side roughness. :'The local"; ..,' r."
<br />..l:;,~,};C':'~'~ bolDldary shear should be increased additionallY in bends as indicated ~ .
<br />,'~~i; : ',?t'> ,in EM UIO-2-160I, 'Plate 34. ., c..'" "'1;'~~l1r\:,,"f""^
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<br />~i;:' , :':;:;:!.::can w~thstand,called the riprap ?~ign shear~should be determined by,~~~.r'1!,-,
<br />~;.',.:;. ,:'-t}' -equauons (33) and (34) for ~e nunlllllDD DSO sue stone. :If the localt~<-~' .~\;
<br />-, ,,'.' botmdary shear is within a xeasonable range of being equal to this":':!J~~;'-t':
<br />';~;i:::', 4iesign sh:ar, the trial riprap stone ~izes are. satisfactory for de. Sign..../;.\.\lj;'.~.;.;..~.~. ';"
<br />.However, ~f the local bOlDldary shear 15 appreCIably greater or less ". h;>l!'......, "(,' ~
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