Investigation of False Positives in Database of Liquefaction Assessment Procedure based on Shear Wave Velocity

摘要

The simplified liquefaction assessment procedure based on shear wave velocity is frequently used for liquefaction potential evaluation. However, a large number of false positives (no liquefaction detected when the V_(s1)-CSR combination indicated that it should have been) in the database on which the simplified procedure was based are a major concern for its reliability. Although some of the false positives might be explained by the presence of a thick surface layer that masks the occurrence of liquefaction, many of them cannot. Theoretical CRR_(field)-V_(s1) combinations for silty sands containing 0 to 15 percent non-plastic fines further confirmed that the existence of false positives is predictable. An important factor is that the liquefaction potential may be more closely related to the medium-to-large strain shear modulus for sands with non-plastic fines, which is not reflected by the shear wave velocity measurement alone. The simplified procedure based on the CPT penetration resistance or SPT blow counts should be more reliable.