Abstract:Loess liquefaction is a disastrous phenomenon which should be carefully treated to reduce the risk. But the relative lacking of both site study results and engineering experience makes it difficult to evaluate liquefaction potential of loess of construction sites. Through many studies carried out since 1990＇s, the understanding for loess liquefaction is improved substantially. As a result, to incorporate of these studies in seismic code became urgent, but at the same time, new proposals on loess liquefaction often face scrutiny from engineers. In order to resolve the difference between laboratory studies and information obtained from field, the two approaches must be combined and any proposal on evaluation of loess liquefaction should at least sound reasonable by applying field test data, which is the backbone for geotechnical analysis. Based on previous studies, this study carried out experiment in laboratory to get understanding of loess liquefaction behavior and the main factors that determined whether the loess sample wound liquefy or not. Then using feedbacks from engineers on accept method for loess liquefaction evaluation, field data of saturated loess site were collected, and the liquefaction evaluation method recommended in Chi- nese ＂Code for seismic design of buildings＂ （ GBS0011 -- 2010 ） （ referred as ＂national seismic code＂ } was examined to validate its suitability for loess liquefaction. Through all these efforts, it is found that the liquefaction of loess cannot be properly evaluated by using the current liquefaction potential evaluation method in national seismic code. And the laboratory test is good at providing preliminary evaluation information on weather loess will liquefy or not under certain seismic in- tensity. For detailed evaluation of loess liquefaction, field data interpretation is more reliable. Based on these understandings, the proposed method on loess liquefaction is a two stage evalua- tion： 1） for Preliminary evaluation of loess liquefaction, the age, clay content, shear velocity, plastic index, degree of saturation should be used to determine weather loess; 2） For detailed e- valuation of loess liquefaction, the principles behind the Chinese code for seismic design of build- ings are still valid, but the criteria should be modified to reflect the actual field test data from sat- urated loess site. It is recommended that SPT reference values or NO, as it represented in national seismic code should be reduced and a set of more realistic values which are respectively for design ground motion0.1 g, 0.15g, 0.2g, 0.3gand0.4gshouldbe7, 8, 9, lland13. This proposal is accepted by expert during the drafting of ＂Specification for seismic design of building＂ of Gansu province （DB62/T25- 3055- 2011）, which is a milestone for liquefaction evaluation of loess sites.
