Abstract:

The coral sand in the project site is mainly composed of coral sand and gravel with wide gradation characteristics, and its coral gravel content is distributed from 20% to 90%. Its liquefaction characteristics are quite different from quartz sand. The application of the current liquefaction evaluation method to the coral reef sand site will lead to the design of liquefaction remediation being uneconomical or unacceptable. In this study, the sands from islands and reefs of the South China Sea and the coral reefs of East Timor were taken as the research objects to conduct the original gradation dynamic triaxial test. A liquefaction evaluation method was developed based on the relationship between the liquefaction resistance CRR and the relative density D_r, and a comparative analysis was carried out through the centrifuge vibration test. The results show that under the same ground motion conditions, the excess pore pressure ratio generated by the dynamic triaxial test is larger than that of the model test; when the duration increases to 30 weeks (corresponding to magnitude 8), the soil liquefaction depth is up to 20 m, which effectively proves that the coral reef sand site has the potential risk of liquefaction under the action of strong earthquakes. In addition, through the calculation of liquefaction discrimination, it is verified that the accuracy rate of the liquefaction evaluation method based on the “CRR-D_r” relationship is 82.5%, and the inconsistent results are conservative for the working conditions, which can be applied to engineering liquefaction mitigation design.

Key words: coral sand, liquefaction evaluation method, centrifuge vibration model test, strong earthquake motion