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i <br /> I �'hc abovc dcsign valuc has a factor of sa(ety of at Icast 3 for dcad plus long-tcrtn live loads. Por <br /> short-tecm transicnl loads(c.g., scismic, wind loads), the allowablc bearing capacity can be incrcased by <br /> Ionc-third if permiucd by ihc dcsign standard. <br /> All exlcrior footings should be founJcd al Icast I8 inchcs bclow thc lowest adjaccnt finishcd gradc, w•hile <br /> I intcrior footings may bc foundcd a minimum of 12 inches below top af slab. Wc rccommend <br /> minimum footing widths uf 16 inchcs nnd 3 fccl far continuous and isoluted footings,respcctivcly. <br /> ILATERAL RESISTANCE <br /> Latcral loads may bc resisted hy friction on the base of footings and the slab and passive rcsistance on the <br /> I sidcs of the footings. Frictional rcsistancc may bc detertnincd using 0.4 for the cocfTicient of base <br /> friction. 1'nssivc rcsistancc mey bc dctertnined using an equivnlent Ouid density of 300 pcf,assuming Ihat <br /> thc soils against thc footmgs for a distancc of twicc thc footing dcpth consist of compacted structural fill. <br /> I Passivc pressurc can bc increascd to an cquivalcnt fluid dcnsiry of 450 pcf, essuming that dense to vcry <br /> dcnsc glacial till is prescnt against U�c foundation.Thc abovc cocf7icicnt of friction and passivic equivalcnt <br /> Ouid dcnsiry valucs includc a factor of safcty of about 1.5. <br /> IRETAINING WALL5 <br /> Laterol Sol1 Pressures <br /> I 'I'he latcral soil prr.ssures acting on rctaining walls will dcpend on thc nawre and dcnsiry of thc soil behind <br /> ihc wall, thc amount of latcral wall movcmcnt that occurs as backfill is placcd, and thc inclination of the <br /> I hnckfill surfacc. I�or walls lhat arc Gcc to yicld at lhc top at Icast two-ihousandlhs of the hcight of thc <br /> wall (i.c., wall hcight timcs 0.002), soil pressures will bc Icss Ihan if movcmcnt is restraincd. Wc <br /> rccommcnd that "frcc" walls supporting horizontal backfill be designcd using an equivalent fluid density <br /> of 35 pcf, and restraincd walls bc dcsigned using an cquivalent Iluid density of 55 pcC The <br /> abovc-rccummcndcd laleral soil pressurcs do not include thc effects of sloping backfill surfaccs or <br /> surchargcs such as tretlic loads or olhcr surface loading. 'The equivalent fluid densiry should bc incrcased <br /> to 50�f for n 2I1:1 V sloping backfill for unrcstraincd walls. <br /> Wc recnmmenJ a seismic surcharge bc opplicd to all permanent rctaining walls. The scismic surchargc is <br /> a unifomi wall pressurc that is addcd lo Ihc static valuc and Uic scismic casc is analyr.cd wilh a rcduccd <br /> factor of safcty(typically I.1 or grwtcr). Wc rccommcnd scismic surchargcs of 1011 psf and I SH psf for <br /> thc yiclding and non-yidding wall conditions, rcspcctivcly. <br /> � Wal!Backflll <br /> I <br /> All backtill li�r rctaining walls should consist of swctural fill as described prrviously with the cxeeption <br /> I that care should be taken lo prevent the buildup of excessivc lateral soil prc�*ures due to overcompaction <br /> ' ol'Ihc backtill bchind Ihc wall. T'his can lx accomplished by plucing the baakfill localcd within 24 inches <br /> of ihc wall in lifts not cxcccding 8 inchcs in loosc thickncss and compacting this zonc with liandoperated <br /> compaction cquipmcnt. <br /> Wad Dralnape <br /> I <br /> � 'I hc rccommended cyuivalent �luid density assumes a free-draining condition bchind thc wall. Pcrtnanent <br /> Jrainagc sysicros should hc providcd to collect waler and prevent the huildup of hydrostatic prcssurc <br /> � ngainst thc wall. Wc rccommcnd that thc drainagc syslcm consist of (1) a 2-foot-widc zonc of <br /> I l�ilrNn.1l14f-11I911.{ PagP7 (�iEOENGINEEIIf� <br /> � Alnc?I.?INW <br />