The primary objective of this study was to develop simple, empirical tools to evaluateliquefaction problems in level and sloping ground. The proposed correlations andprocedures are particularly useful as screening tools because of their simplicity. Specifically,these procedures include:1. CPT-based level ground liquefaction resistance relationships for sandy soils;2. SPT- and CPT-based relationships to estimate the yield shear strength availableat the triggering of liquefaction in ground subjected to a static shear stress;3. SPT- and CPT-based relationships to estimate the liquefied shear strengthavailable at large deformation after the triggering of liquefaction in groundsubjected to a static shear stress; and4. A comprehensive liquefaction analysis procedure for ground subjected to a staticshear stress that addresses liquefaction susceptibility, triggering of liquefaction,and post-triggering stability.The author collected a database of 172 level ground liquefaction and nonliquefactioncase histories where CPT results are available. These cases were separatedinto those involving clean sands (less than 5% fines content), silty sands (between 5 and35% fines content), and silty sands to sandy silts (greater than 35% fines content) todevelop three separate liquefaction resistance relationships based on fines content(percentage by weight passing the U.S. Standard #200 sieve). The proposed relationshipsalso use median grain size (D50) to classify the case histories.The author collected thirty-three case histories of liquefaction flow failure where SPTand/or CPT results are available or can be reasonably estimated. These flow failure casehistories were back-analyzed to evaluate the yield shear strength and yield strength ratiomobilized at the triggering of liquefaction. Relationships between yield strength ratio andcorrected SPT and CPT resistance were developed for use in liquefaction triggeringanalysis. The flow failure case histories also were back-analyzed to evaluate the liquefiedshear strength and liquefied strength ratio mobilized at large deformation. For cases withsufficient information, the stability back-analysis incorporated the kinetics of failure (i.e.,momentum). Relationships between liquefied strength ratio and corrected SPT and CPTresistance were developed for use in post-triggering stability analysis.Lastly, the author proposes a comprehensive liquefaction analysis procedure forsandy soils to evaluate: (1) liquefaction susceptibility; (2) triggering of liquefaction; and (3)post-triggering/flow failure stability. The procedure incorporates the proposed relationshipsto estimate yield strength ratio and liquefied strength ratio, and does not require a suite oflaboratory tests or corrections for sloping ground and vertical effective stress. The procedureis verified initially using the Lower San Fernando Dam case history, and is particularly usefulas a screening tool.
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