Abstract: The sand liquefaction evaluation formulae based on the standard penetration test (SPT) blow count in China’s seismic design code are the most widely used and authoritative liquefaction evaluation formula proposed by Chinese scientists, which are suitable for China’s national conditions. The basic principle of this formula is to use the groundwater level of the site and the burial depth of the saturated sand layer to correct the reference value of SPT blow count to obtain the critical blow count. The SPT reference blow counts in this formulae depend on liquefaction data. However, the database used to construct the evaluation formulae in the codes mainly comes from post earthquake survey and testing data as well as earthquake damage experience of several earthquakes that occurred in China in the 1960s and 1970s, but the data has not been systematically updated. By adding liquefaction data from recent earthquakes in China, the number of liquefaction data is significantly increased. Drawing on the theoretical framework of liquefaction discrimination methods in China’s codes, this paper gives the benchmark values of SPT blow counts under different intensities through data analysis, and constructs a new liquefaction discrimination formula. To verify the formulae, back-judgement on the data were performed, and the results indicate the success rates of the new formulae are fairly satisfactory and keep balance between liquefaction data and non-liquefaction data. The analytical results presented herein can be helpful for revising liquefaction evaluation methods in seismic design codes.

Key words: standard penetration test, liquefaction evaluation formulae, reference SPT-blow counts, liquefaction data