Abstract: China’s water conservancy projects are constructed under complex environmental conditions, including strong earthquakes and thick overburden layers, which exacerbate the challenges in assessing liquefaction of deep-buried sandy soils. Current SPT (standard penetration test) -based liquefaction assessment methods have limited depth applicability, failing to meet engineering demands. This study analyzed the differences between domestic and international SPT-based liquefaction assessment methods, summarized three primary factors influencing sand liquefaction: site environmental conditions, soil intrinsic properties, and dynamic loading characteristics, and investigated their impacts on calculation results. Under ideal site conditions, critical SPT blow count curves for deep-buried sandy soils were calculated using various methods. The results reveal that discrepancies exist in critical SPT blow counts among different methods at identical burial depths due to variations in parameter calculation algorithms. The critical blow count curves demonstrate distinct evolution patterns with increasing fines content or clay content. Under equivalent conditions, the critical blow counts exhibit positive correlations with both seismic magnitude and peak ground acceleration. Existing SPT-based liquefaction evaluation methods show varying applicable depth ranges in international practice. The influence of critical depth or critical effective overburden stress on liquefaction potential assessment for deeply buried sand deposits requires further investigation.

Key words: sandy soil in deep layer, liquefaction assessment, standard penetration test, earthquake