Empirical Correlation of Soil Liquefaction Based on SPT N-Value and Fines Content

Abstract

A critical review of field performance of sandy soil deposits during past earthquakes is conducted with special emphasis being placed on Standard Penetration Test N-values and fines content. The field relationship between adjusted dynamic shear stress ratio and normalized SPT N-values together with laboratory tests on undisturbed sands indicate that (1) sands containing more than 10 percent fines has much greater resistance to liquefaction than clean sands having the same SPT N-values, (2) extensive damage would not occur for clean sands with SPT N1-values (N-values normalized for effective overburden stress of 1 kgf/cm2) greater than 25, silty sands containing more than 10 percent fines with SPT N1-values greater than 20, or sandy silts with more than 20 percent clay, and (3) sands containing gravel particles seem to have less resistance to liquefaction than clean sands without gravel having the same SPT N-values. On the basis of the above findings, an improved empirical chart separating liquefiable and non-liquefiable conditions is presented in terms of dynamic shear stress ratio, SPT N-values, fines content, and shear strain amplitude.