Applicability and reliability of CYY formula based on Chinese dynamic penetration test for liquefaction evaluation of gravelly soils

The CYY formula, proposed by Cao, Youd and Yuan in 2013 and based on the field investigations of gravelly soil sites liquefied during the 2008 Wenchuan earthquake using the Chinese dynamic penetration test (DPT), has uncertainty regarding applicability and reliability in practical use. Nevertheless, the DPT has obvious advantages in maneuverability and economy. In order to verify the reliability, accuracy and practicability of the CYY formula, 29 new gravelly soil sites in total, 26 of which are liquefied during 6 different earthquakes including the 1964 Alaska earthquake in America, the 1976 Friuli earthquake in Italy, the 1983 Borah Peak earthquake in America, the 2008 Wenchuan earthquake in China, the 2016 Muisne earthquake in Ecuador, and the 2016 Kaikora earthquake in New Zealand, are selected for China-U S joint borehole drilling and DPT. The field tests at 14 sites in the Chengdu Plain are mainly completed by the Chinese side, and the rest of tests are mainly completed by the US side led by Professor Rollins. The results indicate that the Chinese DPT is feasible in different countries and can effectively penetrate about 20 meters of gravelly soils, and the blow count of DPT can be used as the primary index for predicting the liquefaction of gravelly soils. The 26 selected liquefaction sites consist of soil profiles in undrained conditions