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<br /> TABLE 7. Approximate maximum backfill loads (in Ib, per lin. ft.) on concrete trench conduits'
<br /> Saturated clay(Kµ=0.110 anA w= 130 Ib./cu.ft.)
<br /> Width oi trench at top of conduit(in�eet)•'
<br /> HY
<br /> 2 3 4 5 6 7 8 9 10
<br /> 4 800 1,300 1,900 2.400 3,000 3,400 4,000 4,500 5,000
<br /> 6 1,110 1,900 2,fi00 3,400 4,300 5,100 5,900 6,800 7,400
<br /> 8 1.300 2,400 3,300 4,400 5,400 6,500 7,600 8,700 9,800
<br /> 10 1,500 2,800 4,000 5,200 6,600 7,800 9,100 10,500 12,000
<br /> 12 1,700 3,100 4,500 6,000 7,500 9,100 10,700 12,200 13,900
<br /> 14 1,800 3,300 5,000 6,800 6,500 10,300 12,100 14,100 15,900
<br /> ', 16 1,900 3,600 5,500 7,400 9,400 11,500 13,A00 16,600 ll,700
<br /> � 18 2,000 3,900 5,900 8,000 10.200 12,600 14,700 17,100 19,400
<br /> 20 2,300 4,100 � 6,200 8,600 I1,00� 13,500 16,000 18,400 21,000
<br /> 25 2,200 4,400 7,000 9,700 12,600 15,700 18,700 21,800 25,000
<br /> 30 2,300 4,700 7,600 10,800 14,000 !7,500 21,200 2A,800 28.400
<br /> •By the Marston lormula W=C�wB�;surlace loatls not includetl.
<br /> �•Whero wid�h of lrench e:ceeds ihe transilion wid(h lor the inslallalion,the transition wlElh shall govem(see page 3l).
<br /> }H=depth of fill to top of cantluit(in It.).
<br /> TABLE S. Approximate maximum backfill loads (in Ib, per lin. ft.) on concrete trench conduits*
<br /> i Sand and gravel (Kµ-0.165 and w- 1201b./cu.ft.)
<br /> I� Width o(trench at top of canduit(in fect)••
<br /> H}
<br /> 2 3 4 5 6 7 8 9 30
<br /> 4 700 1,100 1,600 2,300 2,600 3,100 3,500 4,000 4,400
<br /> ti 900 1,500 2,200 2,900 3,600 4,400 5,000 5,800 6,600
<br /> 8 1,000 1,900 2,800 3,700 4,ti00 5,500 6,500 7,500 8,A00
<br /> 10 1,200 2,200 3,200 4,300 5,5G0 6,fi00 7,800 D,900 10,200 �
<br /> 12 1,200 2,400 3,600 4,900 6,300 7,600 9,000 10,400 11,800
<br /> 14 1,300 2,500 4,000 5,400 7,000 8,500 ]0.100 11,700 13,300
<br /> . lfi 1,300 2.700 4z00 5,900 7,6U0 9,400 11,100 13,000 14,800
<br /> � 18 1,400 2,800 4,500 6,300 8,200 10,300 12,000 14,100 16,200 '
<br /> i
<br /> � 20 1,400 2,900 4,700 6,600 R,700 10,800 13,000 15,200 17,400
<br /> ' 25 1,400 3,000 5,100 7,300 9,700 12,?00 14,900 17,600 20,300
<br /> i
<br /> i 30 1,400 3,300 5,300 7,800 30,600 13,400 16,500 19,500 22,800
<br /> •Bytha Marslan lormula W=CywB�;surlace loads not IncludeA.
<br /> ��Whern witlth of lrench exceetls the transition widlh lor the installation,�he lransilion widlh shall 6avern(see page 31).
<br /> }H=dep�h of lill lo�op ot tontluit(in It.).
<br /> method in rvhich the conduit is Ixdded witli ordinary part of the conduit exterior or to fill all spnces imder
<br /> i enrc in an enrth Poundatioi� shaped to fit [hc lower pnrt nnd around the conduit with granulnr materinls. This
<br /> I of thc conduit exterior with rensonnble cloxness for at type oC bedding also includes rock foundation in wliich
<br /> lenst 10 percent of itx hcight. 'Phc remainder of the nn e:uth cushion is provided under thr, conduit but is so
<br /> � conduit is surrounded by grnntdar malerials placcd by shallow 6haL the conduit, as it settles imder the influ-
<br /> shovcls to fill all spnces completely uuder and adjacent ence of 6he vcrtical lond, npprouclics contact widi the
<br /> tu thc wnduit. In ca:e of rock (oundutions, thc conduit rock.
<br /> is bedded on n care[ully shuped earth cusliion oP the Load factor
<br /> snme depth as provided mider Cinss 13 bedding, wit6
<br /> the eurth miilerinl carefully I;lamd around Uic canduiL �1'hc load or brdding Gtctors for projecting coudui�s :trc
<br /> Clas, D, impermis�ible projectin� oond�ut bedding, espressed by the formtda /,�= 1.431
<br /> is thnt �nctLud in �chicL little or un �•:tre is escrciscd N-zq
<br /> cithcr to shiipc thc (oundaliun sivfuce Lu fit tl�c lo�scr «hrro l.t = thu load factor
<br /> 34
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