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�'LV-/_.j-y0 LI : J:J!\ IV�_ �.��il� �.li�. . • .� �. r�. \�'�" / <br /> Glcnwood Terracc <br /> Filc Number I?6494 <br /> May 12, 1994 <br /> Page 14 <br /> Although stn�ctural loading infomiation was not availablc at lhc time of lhis study,bascd on our experience <br /> of mulli-family residential slructures supporteci on similar soil conditions and for Uie above allowable soil <br /> bearing pressures, wc cston�te that 11ie maximum total post�onslruction sctticment should be 3/4 of an <br /> inch or Icss,nnd that the differentia!scttlement across Ihe building width sliould be 1/2 inch or less. <br /> Latcral loads can be rcsisted by 1'riction bchveen the Counda�ion and subgradc or thc passivc carth pressure <br /> acting on U�e below-gradc foundalion. For the lattcr, the foundation must be placed "neat" against the <br /> undisturbed soil,or back filled wiUi a clean, fi'ee-draining, tompacted structural fill. We recommend that <br /> an cquivalent Iluid wcight (EF� of 250 pounds per cubic foot (PCF) for tlie native soils and structural <br /> fill; and 100 PCP for lhe cxisling fill be usrd ro dMenninc tlic allowable latcral passive pressure. M <br /> allowable ccefficicnt of friction 6etween footing and native soils of 0.35 may be uscd. 'Iliese values include <br /> a factor of safcty of I.S. <br /> Conventionel founJation with Control Uensity Fill: '(lie foundation systcm could bc placcd on CllF <br /> which cxtends in�o dic underlying native soils. 7lie use of CDF reduces die hcight of foundation stem w�lls <br /> that cxtend to bcaring soils. 'Ilie CD�should bc placed in a manncr that will provide adequatc bcaring and <br /> allow construclion of a convcntional footing bcaring on top of it. 'Ihe CDP is a low strength concrete <br /> praluct with high flow capabilitics. A trench is excavatcd to cxposc bearing soils and dic CDF is pourcd <br /> up to the desired bottom of fooling elevation. If caving condilions are encountered, tlie use of CDF <br /> becomes Iess cost-cffcctivc as a larger vofumc is rcquircd. Typically,du trcnch is cxcavatcd and the CDF <br /> is pourecl inunediately to reduce die exposuro to caving. In severe caving conditions, tlie Icngth oFtrenches <br /> should be shortened and in some cases, the final cleaning of tlie excavation is accomplislied with some CDF <br /> already in place. Thc placement of the CDP should be observed by a representative of this office. <br /> laleral loads can be resisted by friction beh��een lhe foundation and ilie CDF or subgradc. M allo«�able <br /> cocRcicnt of friction bch�cen founJation and tl�e CDG of 035 may be uscd. 71ic value includes a fnctor of <br /> safcty of 1.5. <br /> Auger Cast-in-Place Piles: Our explorations did not exlend Uvough the fill at all locations. The depth lo <br /> bcarins soils should be determined prior to placemcnt of production pilcs in Uiese arcas. 'ihis may bc done <br /> by cithcr grntccLnical borings or by pulling thc pilc insG�llation auger�vithout grouting. Tlro soils obscrvcd <br /> on thc augcr and tticir position on the augcr would be used ro estimalc tlic dcplh ro the bottom of dw fill. If <br /> tlie latter is to be used, it should bc cicarly spelled out in Qic contract documents as it is usuully an cxtra for <br /> die piling contracror, yid somc contractors H�ill simply not do it. \Vhen pulling the auger, lhe auger should <br /> continue to spin��ery slo�el��so as not to advnnce tlie soil significvitly up ll�c (lights. <br /> NELSON-COWRETTE & AS50CIATES, INC. <br /> PFI�-23-19% 1?_�[�9 2�76 481 2510 96i P.16 <br />