In this paper, known simplified methods for the assessment of soil liquefaction are summarized. Their discrepancies are examined. Using the Chi-Chi earthquake data as well as other reported data, a set of three critical cyclic strength curves were obtained by finding the minimum of misclassified points. The functional forms of these three curves are an exponential function, a hyperbola, and a cubic polynomial. A lower bound critical cyclic strength curve is then established. This curve may have important applications in practice for liquefaction-related designs. Through this case study, it was found that a minimum cyclic strength CSRlim may exist at a very low value of (N1)60. An upper limit (N1)upp60 also exists beyond which liquefaction may not occur. Furthermore, current simplified methods seem suitable only for a limited range of N values and fines content, and may fall for general applications. The lower bound curve proposed in this paper may provide and alternative approach for improvement. Since the explicit functional form and the statistical indices are available, the statistically regressed curves seem to have a benefit in that it may be used directly to conduct hazard analysis, and evaluate the uncertainty within the critical cyclic strength curves.
- Chi-Chi earthquake
- Critical cyclic strength curve
- Minimum of misclassified points method
- Soil liquefaction