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<br />earthquakes affec ting the site by magnitude and epicentra1 <br />distance. A rapid evaluation of the possibility of <br />liquefaction can be made by examining the considerable <br />body of information existing which documents known cases <br />of liquefac tion and no liquefac tion during earthquake- <br />induced ground motion. This information should be used to <br />help determine liquefaction possibilities. <br /> <br />A procedure wide 1y used in determining the liquefaction <br />potential of natural deposits is to estimate resisting <br />capacity from standard penetration tests and compare this <br />to the required capacity as determined by empirical <br />correlations or analytical methods. For enbankment or <br />foundation materials that can be effectively sampled and <br />tested, the cyclic and/or steady state strengths of <br />material may be determined by laboratory testing and <br />compa red to the requ i red streng th s de termined by <br />analytical or empirical procedures. <br /> <br />(3) Pseudostatic Analysis <br /> <br />A pseudosta tic ana 1y sis (some time s called seismic <br />coefficient analysis) should only be considered as an <br />indication of the seismic resistance available in a <br />structure, and then only for structures not subject to <br />significant dynamic response or bui1d--up of pore pressure <br />due to shaking. <br /> <br />Studies of earthquake-induced slides show that the method <br />does not always predict failure where failures have been <br />found to occur in enbankments consisting of sandy soil or <br />constructed on sandy foundations which show a marked loss <br />of strength due to earthquake shaking. Pseudostatic <br />analysis is not a reliable procedure for evaluating the <br />possible performance of dams and foundations of these <br />type s 0 f soi 1s. However, it ha s been shown tha t when <br />applied to soils which show no significant loss of <br />strength or pore pressure development due to earthquake <br />shaking (usually clayey soils, dry sands, and some dense <br />saturated sands), the procedure will generally provide an <br />acceptable method of ensuring adequate performance for <br />enbankments if mininum safety factors for corresponding <br />levels of acceleration are achieved. <br /> <br />(4) Newmark-Deformational Analysis <br /> <br />Severa 1 procedu re s are avai lab 1e for carrying ou t the <br />basic Newmark-type deformational analysis. Two steps in <br />this ana lysis are required. The first is to obtain the <br />response of the structure to the earthquake ground motion <br />and the second is to make the displacement calculations on <br />one or more potential sliding masses. Various methods <br />are available for calculating the response and <br /> <br />-25- <br />