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

The CYY formula, presented by Cao, Youd and Yuan in 2013 and based on field investigations of gravelly soil sites that 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 liquefied during six different earthquakes including the 1964 Alaska earthquake, America, the 1976 Friuli earthquake, Italy, the 1983 Borah Peak earthquake, America, the 2008 Wenchuan earthquake, China, the 2016 Muisne earthquake, Ecuador, and the 2016 Kaikora earthquake, New Zealand, were selected for China-U.S. joint borehole drilling and Dynamic Penetration Tests. While the field tests at 14 sites in the Chengdu Plain were mainly completed by the Chinese side, and the rest of tests were mainly completed by the U.S. side led by Professor Rollins. The results indicate that the Chinese Dynamic Penetration Test is feasible in different countries, can effectively penetrate about 20 meters of gravelly soils, and 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 and are consistent with the presented threshold triggering condition for the occurrence of liquefaction in gravelly soils. The verification rate for the CYY formula is around 96%, indicating that the CYY formula has high reliability and can be used to predict the potential for liquefaction in gravelly soils in different countries after necessary corrections such as hammer energy, overburden pressure, earthquake magnitude, etc.