Evaluation of liquefaction potential of saturated sands based on piezocome penetration tests on resistivity

The liquefaction of saturated soils is a major concern for the earthquake damage of foundation, and its effective evaluation is rather important. Because of the difficulty and cost constraint of obtaining high-quality undisturbed samples, in-situ testing is commonly applied to evaluate the potential of soil liquefaction. At present, numerous methods based on the cone penetration test (CPT) have been developed, but none of them has been accepted to be the most reliable one. In high risk projects, a comprehensive evaluation based on various methods is usually adopted, and thus the research on new method to evaluate the liquefaction is still necessary. The resistivity of saturated silts and sands is measured using resistivity piezocone penetration tests for the construction of Suqian-Xinyi expressway. First, the relationship between normalized cone tip resistance and resistivity is analyzed and can contribute to the evaluation of soil liquefaction based on resistivity. Second, the study on combination of resistivity and soil behavior type index to directly calculate the cycle resistance ratio (CRR) is conducted with the CRR from Robertson modified liquefaction evaluation model as a reference. The influence of thin cohesive layers and transition zones is also analyzed. It is shown that the resistivity and soil behavior type index can be used for effective evaluation of liquefaction potential of saturated soils. The accuracy of the proposed method is distinct when the cone passes soil interface since the vertical resolution of resistivity is directly proportional to the distance between outer electrodes. Otherwise, the proposed method is not suitable to thin clay layers and transition zones as it may underestimate CRR.