Assessing and managing the risk of earthquake-induced liquefaction to civil infrastructure - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 116

Liquefaction

CRR curve for
clean sands

CSR

No liquefaction

in-situ
test measurement
(e.g.

Corrected

N 160 , q c1N , V s )

5.3 Schematic diagram showing the simplifi ed approach for assessing
liquefaction potential of a soil.

the evaluation of the liquefaction potential and hence the corresponding
empirical charts are based on a larger set of case histories. On the other
hand, the Cone Penetration Test (CPT) provides continuity of data over
depth which allows the identifi cation of even thin liquefi able layers. Given
the degree of uncertainty and approximation in both procedures, ideally
the SPT-CPT correlations should be used as complementary information
rather than following only the one or the other. The Becker Penetration
Test (BPT) database is rather limited as this test is only used in soils with
large particles (e.g. gravels), where SPTs and CPTs cannot provide accurate
results, while the shear wave velocity ( V s ) measurements are used more
rarely either in absence of other data or to complement the CPT or SPT
based evaluations.
Since the early work of Seed & Idriss (1971, 1982) and Seed et al. (1985),
numerous empirical correlations and modifi cations of the employed empiri-
cal correction factors in the liquefaction evaluation process have been
proposed in the literature. Youd et al. (2001), based on the fi ndings of two
workshops on evaluation of liquefaction resistance of soils (1996 NCEER
and 1998 NCEER/NSF workshops), provided updated SPT, CPT and V s
correlations. Since the state-of-the-art summary by Youd et al. (2001), the
database has been enhanced with a number of case histories from more
recent earthquakes and therefore a number of studies have attempted to