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<br />. ETL 1110-2-120
<br />14 May 1971
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<br />(3) If pockets of smaller stones are present, the strength
<br />.the riprap material in these pockets may be determined by using
<br />spherical diameter of the average size stones in equation (33).
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<br />(4) A gradation which is deficient in smaller stones will 'have
<br />an excessively irregular surface and openings may traverse the layer
<br />from top to bottom. In this case, an increase in layer thickness and
<br />coarser bedding material which would not pass through the voids should
<br />be used. The strength of the rip rap material may be determined by
<br />using a stone size diameter somewhat less than the average size, based
<br />on judgment, in equation (33). .
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<br />of
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<br />(5) Careful examination should be made of the in place position
<br />of elongated and/or slabby stones 'which fail to meet the shape"""
<br />criteria. If these stones are well keyed rather than lying loosely <};,';:. .,:
<br />01\ the surface and the provisions of subparagraphs (1) and (2) above . ~~'..1.',.>
<br />are satisfactory, the material should be acceptable. .Elongated and/or -,'
<br />slabby stones which lie on the surface should not be considered as. ..,':;'~~"i/'"
<br />.~~~tributing to riprap strength. ~-:;C:~l;'i0.:~~~i~ '~!~;
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<br />. "", (6) Other reasonable assumptions' should be made based on experience' 'is'
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<br />and judgment. For example, if riprap material from a quarry can be,;'~'\W;>
<br />correlated with previously tested and accepted materials from similar '{;/J:
<br />'<type quarries, it may be possible to establish reasonable design. '. ..' ,':;/~."
<br />strength and specification requirements for the material. ';:;:i~;~i" ',;.fl\:~.i;' ~
<br />of '.<' .~ ..'\.'i;-'" (".~,,':.
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<br />In SUl1llllary, the discussion in this paragraph emphasizes the need, to;:'~"i;
<br />" supplement the guidance given in EM 1110-2-1601 with the considerations, l,,:~'
<br />. outlined above, in order to specify riprap shape factors, gradation . J"'" Jir,:
<br />. . limits and layer thickness', as well as to determine riprap strength. ,$ '. -
<br />,'.' ....This discussion also applies 'to 'the use of "quarry run" material for' .
<br />riprap protection. i':-',.,. . ":'t~:~ n.: ' " ," "~;' ~.
<br />_~"':'"'---;~- '1 "~~r~~~!,. ~.'~' ~~~ .'f(.l .~ :,,~'" )~ ~'~;.'
<br />. b. Design Aids. ,,;Inclo.sures Lt4rough 3.ai'e tables showing riprap '" " ','
<br />gradation limits for various. specific weights. (SSD), layer thicknesses '~c'.,., . 1>~':
<br />and design factors as follows::'/;v'~' .... ,,:..,> . ;;-, ,":". . ":t;;4'\;'
<br />, ,,~:~:_~.~. '. _~' ..- .~_> l~'(~.":~f"~<:~fJl~~:!.::~'!:.~~;:~-~'::'-:' . "." ' .' '.. ~ ,::~'i~i:::Y;:~. . )S';; ~~~~~:
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<br />d". para~~p~~n~~~s:~'~, c~~~::io~~~ (~) .d~:s~gnfactors indi~ate~\"t~,.~;'}' . 'G'.:I:: . .:
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<br />. ',,-.4;:~~:(2)' ryi~~;~;'::<;>co~~;~nd~' ;o){~rt;:-~~~ factors~n~i'~!~t~ .. '~*'*~
<br />. "~:-"subParag~~:h.~4~~~}::"~'!.J;i:',"" ,.;;;~f.;: ". .':-t..,. ."..~,; -.::{~;:f:~;"'1;'-,r .' '~~.'~
<br />. , (3)' Inclosure 3 duplic~tes in~losure 2 ex~~pt that' the W50 maxi-.\..... '?fJJ;.':~
<br />'~ theoretical stone di~eter ~s. on~-h~lf the increased la~er;',. :;:-<?;ii;,: :'~:}
<br />th1ckness and the WlS maxl.DlUm l1m1t 1S 1ncreased correspond1ngly. ,~l<:' ",k'
<br />Riprap material corresponding to these gradation limits should be co~~_~ ~
<br />sidered when placed in the dry at ~?cations subject to turbulent flow .:t~:' "-,-
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