Evaluation of Liquefaction Susceptibility for Microzonation and Urban Planning

Various procedures were developed to evaluate liquefaction susceptibility of soil layers for implementing engineering remediation measures. The approach that has gained wide acceptance within the framework of urban planning is to establish microzonation maps with respect to liquefaction susceptibility to mitigate possible earthquake damage related to liquefaction. In this context, microzonation maps were produced recently for six municipalities in Turkey as a part of a major Pilot Project. Two variables are required for the assessment of liquefaction resistance of sandy soil layers; the seismic demand expressed in terms of cyclic stress ratio, CSR; and the capacity of the soil layers to resist liquefaction, expressed in terms of cyclic resistance ratio, CRR. The approach adopted to perform microzonation maps for liquefaction susceptibility was based on the procedure proposed by Youd et al., 2001 and Iwasaki et al., 1982. The variation of the safety factors with depth were determined for each representative borehole where CSR is calculated using stress reduction factor and CRR based on SPT blow counts. In addition CSR was calculated based on site response analyses. The results are compared and the source of uncertainties and the effects of the two approaches are discussed in terms of the final microzonation maps