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Abstract Although the in-situ shear wave velocity tests have been used commonly as engineering testing techniques and shear wave velocity Vs has gradually become a basic index for soil liquefaction evaluation，the in-situ Vs-based liquefaction assessment methods for gravel soils are not available so far. The significant phenomena of gravelly soil liquefaction in the 2008 Wenchuan 8.0 Earthquake are investigated and the in-situ Vs structures for 45 sites in the event are obtained. In terms of the investigation data，the Vs-based approach for liquefaction evaluation of gravel soils is presented and the existing Vs-based methods for evaluating sandy soil liquefaction are inspected. The liquefaction discrimination of gravel soils can be divided into the two steps：the preliminary evaluation and further evaluation. In the preliminary step the geological ages，the buried condition of gravel soil layer and gravel contents of gravel soils are considered and five parameters including seismic intensity，reference values of Vs with depth of gravel soils，groundwater table and gravel content of gravel soils are concerned in the further step. The reference values of Vs as well as the influential coefficients of gravel soil depths and groundwater levels are deduced by normalization method and optimization method respectively. As the type of gravel soils differs from the sandy soils，the densities of two type soils even for the same Vs value are different. If the existing liquefaction assessment procedures for sandy soils are employed，the liquefaction resistance of gravel soils will be significantly overestimated，which means that the methods of liquefaction evaluation for sandy soils are not suitable for gravel soils. The proposed method is noticed with clear expression and high success ratio of regression discrimination；and it can easily be used in engineering practice and code revision.
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Received: 13 December 2009
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