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( i LSI Adapt, Inc. <br /> presentcd in Table 3 and incorporate a safety factor of at Icast 1.5, Which is commonly <br /> applied to transicnt or scismic loading conditions. It should be not�u that these passive <br /> pressure values havc bccn rcduced by a factor of 0.60 (60 percent of rypical valucs for <br /> levcl ground surface condition), to account for thc ncarby, existing, 3H:1V slope <br /> conditions on the east sidc of the proposcd cquipmcnt platfom� location. Thcse valucs <br /> are expresscd as an cquivalcnt fluid unit wcight to re(lcct thc lincar incrcasc with depth <br /> and may be assumed to act ovcr an arca mcasuring two pier diamctcrs widc by cight pir.r <br /> diamctcrs dccp: <br /> Tablc 3 <br /> Allowablc Drilled Pier Passive Pressures <br /> Depth (fect) Allowable Passive Pressure(pcQ <br /> 0-2 0 <br /> 2-3 200 <br /> 3-8 250 <br /> • Suberade Reaction Mcthod: The subgrade rcactiun method is typically used to compute <br /> latcral design loads based on allowable lateral dcflcetions. Using tliis mcthod, tl�e soil <br /> rcaction pressure(p) on thc facc of thc picr is related to thc latcral displacement (y) of thc <br /> picr by thc horizontal subgmdc modulus(kn); this rclationship is expresscd as p=khy. <br /> Bccausc soil modulus valucs arc based on small scalc, bcam load tcst data, and arc <br /> usually repoRed as a.vertical subgrade modulus(k,.), the}'must be comerted to liorizontal <br /> subgrade modulus valucs representativc for largcr scalc applications (such as large picr <br /> diamctcrs) by mcans of various scaling factors, as discussed bclow. In addition to thc <br /> scaling and toading orientation, the soil-pier intcraction governing k;, is also affected by <br /> the soil type,as follows: <br /> • SAND and Sotl CLAY: For cohcsionlcss soils (sand, non-plastic silt) and soft <br /> cohesive soils (clay, cohesive silt), thc horizontal subgrade modulus (kh) <br /> incrcases linearly with dcplh (z). This rclationship is cxpressed as ]y, =nhz(IB), <br /> whcre nh is thc coefficicnt of horizontal subgradc rcaction and (1/B) is lhe scaling <br /> factor. <br /> • Siiff or Flard CLAY: For stiff or hard cohesive soils (clay, cohesivc silts), thc <br /> liorizonlal subgrade modulus (kh) is cssentially thc samc as the vcrlical subgradc <br /> modulus (k,) and is considcrcd constant with depth. This rclationship is <br /> expresscd as ki,=k,[I((i)/1.SB], whcrc [I(ft)/1SB] is thc scaling factor (B is <br /> cspresscd in fcet). <br /> Neztel Go Tetra Tech June 25,2004 <br /> LSI Adapt Project No.WA04-11499-GEO Page� <br />