Development of normalized liquefaction resistance curve for clean sands

We present empirically derived liquefaction resistance curve from a large database of measurements from published literature and also simple shear tests that were performed in this study. The data measured from simple shear and triaxial tests are separately compiled. The data are fitted with two empirical models to develop representative liquefaction resistance curves. Comparisons illustrate that the slope of the widely used power law is highly dependent on the range of data it is fitted to and that the power law underestimates the resistance at high number of cycles (N). The alternative empirical model is demonstrated to provide favorable fit with the measurement over a wide range of data. The representative curves are normalized by the equivalent number of uniform cycles for a magnitude (M) 7.5 event (N-M=7.5) to reduce the wide scatter of the measurements and to make it usable with liquefaction triggering charts that relate in situ parameter with cyclic resistance ratio for a M = 7.5 event. Comparison with published liquefaction resistance curves show that the proposed curve is lower at N <= N-M=7.5 and higher at N > N-M=7.5. A single-parameter empirical exponential function that closely fits the normalized liquefaction resistance curves and representative values for its parameter are presented. We also propose an empirical equation to correct the liquefaction resistance curve measured from a triaxial test to match that from a simple shear test.