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�'1� Valota Road 5-Lot Residential Development Decer 8.B. - Page 127 <br /> � <br /> �� <br /> where CRR7.5 is the cyclic resistaz�ce ratio �or a magnitude 7.5 earthqua�ce and MSF is the <br /> magnitude scaling �ac#ar. The soil layer is considered to be liquefiable if the CRR and CSR <br /> established �or the soil stratum at a given depth, allow a factor of safety against liquefaction, <br /> CRR/CSR, less than the selected factor of safety for the project. A general guideline from the in <br /> selecting an ap�ropriate factor of safety for a project i� shown in the table below (Martin and <br /> Lew, 1994): <br /> Canse uence of Li nefaction NI 6o clean sand Factor of Safe <br /> Settlement <1 S 1.1 <br /> >30 I.0 <br /> Surface Manifestation <_15 �.2 <br /> >30 �.0 <br /> �,aterai Spreading <15 I.3 <br /> >30 I.0 <br /> The variables discussed in the above text a�re u�ed ta develop a pxofle of the soil and a cozx�puter <br /> spreadsheet analysis is ca�rried out to dete�ine lique�'acfiion triggering, liquefaction settlement, <br /> and seismically ind�ced sett�eznent. <br /> Results af Analvsis <br /> Tn general, tk�e site is underlain by fine grained soils with 1ow liquefaction �usceptibali�y and <br /> occasional sand lenses which are highly susceptible to Iiquefaction. Free water was encountered <br /> in owr subsurface exploration at 20 feet belaw the s�rface with reported graundwater as shallow <br /> as 1S fe�t based on data obtained from a report by Terrasearch {1995) for the adjacent praperty to <br /> tl�e east. For the purposes of this analysis, groundwater was xxaod.eled at 15 feet to siznuJ.a�e high <br /> water conditions. The peak ground accelezatzons used in the analyses were talcen as SpS/2.S <br /> (=O.SSOg)per Paragxaph 1802.2.7 o�the California Building Code (2007 Edition). <br /> The granular silt layers located approximately at 35 to �-0 feet below surface grade are susceptzb�e <br /> to settZement during a seismic event. 4ur analysis indicates that the total settlement is estimated <br /> to be on the order of I.09 inches (Figure C1}, with 0.02 inches attributed to dry sand subsidence <br /> and 1.07 inches attributed to liquefaction reiated sei#lement. <br /> 7 <br />