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� Valota Road 5-Lot Residential.Development Decer.$�B� - Page 125 <br /> � <br /> �i <br /> MCE Short Te�n Spectral Response Parameter- SMS 2.062g(FaSs} <br /> MCE 1 Second 5pectral Response Parameter- S�r 1385g(F„S,) <br /> Design Short Te�zn SpectraI Response Paxazzaeter- SDS 1.375g(2/3)SMs <br /> Design 1 Second Spectral Response Param�ter- SD� 0.923g{2/3)S�i <br /> Peak Ground Acceleration(PGA)for liquefaction analysis O.SSOg(SD�/2.5) <br /> Liquefaction Ana�ysis <br /> Soil liquefaction is a phenomenon where saturated granular soils near the ground surface undergo <br /> a substantial Ioss of strength due to increased pore water pressure resuiting from cyclic stress <br /> applications induced by eart�quakes or othex vib�ratio�s. In this process, the soil acquires <br /> mobility sufficient to permit both vertica� and k�ozizantal naoveinents, if not confined, wl�zch�ay <br /> � result in sigz�ificant aeformations. Soils mast susceptible ta liquefactian are loose, uniformly <br /> graded, f ne-grained sands. Tn addition, recent literature indicates that fine grained soils may also <br /> be susceptible ta liquefaction or cyclic strain softening. Examples of highly suscep�ible fine- <br /> grained sail inciude "nonplastic silts and c�ayey siits of low plasticity (PI�12} at high water <br /> content to �iquid 1'amit ratios (w�LL>0.85}." Examples of soils rrioderately susceptible to <br /> liquefaction include "clayey silts and 511� clays of moderate plasticity (12<P7<18} at <br /> w�/L,L>0.$0" (Bray and Sancio, 2006}. It is generally acknowledged that iiquefaction wiil not <br /> occur if these deposits are located at a depth grea�er than 50 feet below the ground surface. In the <br /> deeper deposits, the g.reater overburden. pressure is su�ficient to prevent liquefaction frozn <br /> occurring. <br /> The liquefaction analysis at the sub�ect site was evaluated using the methodology suggested in the <br /> X 996 and 1998 National Center for Earthquake Engineering Research workshops (NCEER) on <br /> evaluation of liq�efaction resistance of soils (Youd & Id�riss, editors), arid the 1999 Southezr� <br /> California Earthquake Center (SCEC} "Recommended Procedures for Iz�n.plementation o�DMG <br /> Special Publicatian I17". A brief outline about th� variables involved in the liquefactian <br /> evaluation process is descrabed below. <br /> One of the steps of liquefaction potential evaluation consists of norrnalizing �he SPT blow cau.z�t <br /> to the effective overburden stress of 100 Kpa or 1.044 tons per square foot. This is denoted N��sa� <br /> and is found through the following formula: <br /> Nl�bo�=Nm C�GECsC�CS <br /> Nm = measuz-ed standard penetration:zesista�ce <br /> 5 <br />