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LSI Adapt, Inc. <br /> End Bearing Capacitics: We rccommend that the drillcd pier penetrate at Icast 10-feet bclow the ground <br /> surfacc. For vertical compressivc soil bcaring capacity, we recommend using the unit cnd bearing <br /> capacity presented in Table 1 below, where B is the diameter of the pier in feet and D is the embcdmcnt <br /> dcpth below thc bcaring soil laycr in fcet. This allowable end bcaring capacity includcs a minimum <br /> safcty factor of 1.5. <br /> Tablc 1 <br /> Allowable Drilled Pier End Bcaring Capacity <br /> Depth(feet) Ailowable Bearing Capacity(ts� Limiting Point Resistance(tsQ <br /> 8 3DB 5 <br /> Frictional Caoacities: Por frictional resistance along thc shaR of the drillcd picrs, acting both do�mward <br /> and in uplift, we reconunend using the allowable sl:in friction value listed in Table 2. Wc rccommcnd <br /> that frictional resistancc be ncglected in the uppermost 2 fcet bclow the ground surface. Thc allowablc <br /> skin friction values prescntcd includes a minimum safety factor of 1.5. <br /> Table 2 <br /> Allowuble Drilled Pier Skin Friction Capacities <br /> Depth (fect) Allowablc Skin Friction(tsQ <br /> �-� 0.0 <br /> Z-3 0.25 <br /> 3-R 0.50 <br /> Lateral Ca�acities: Drilled pier foundations are typically rigid and act as a polc which rotates around a <br /> fixed point at depth. Although morc compicx and dctailcd analysis are available, cither the simplificd <br /> passivic earlh presstrre medmd or Uic subgrade reaction med�od is typically used to dctcrminc thc picr <br /> diameter and depth rcquired to resist groundlinc rcaction forces and momcnts. Thcse mcthods arc <br /> describcd bclow. <br /> • Passivc Earth Pressurc Mcthod: Thc passivc carth pressure mcthod is a simplificd <br /> approach that is gcncmlly used to cstimate an allowable lateral load capacity based on <br /> soil wedgc failure thcory. Althaugh thc lateral deflcction associatcd with thc soil wcdge <br /> failure may bc cstimatcd, design latcral deflections using the passivc carth pressure <br /> mcthod should bc considcrcd approsimatc, duc to the simplificd namrc of thc method. <br /> According ro thc NAVFAC Dcsign Manual 7.02 (19SG), a latcral deflcction cqual to <br /> about 0.001 timcs thc picr Icngth would bc rcquircd to mobilizc thc allowaUlc passivc <br /> pressurc presented bclow; l�igher de(lections �vould mobilizc highcr passive pressures. <br /> Our rccommcndcd passivc carih pressures for thc soil laycrs encountcred at this sitc arc <br /> Ne�nel Uo Tetra Tech June 25,2004 <br /> LSI Adapt Project No.WA04•11499-GEO Page 8/ <br />