Civil Engineering Reference
In-Depth Information
FIGURE 7.1
Chart for estimating the ground surface settlement of clean sand as a function
of the factor of safety against liquefaction FS
L
.
To use this figure, one of the following proper-
ties must be determined: relative density
D
r
of the in situ soil, maximum shear strain to be
induced by the design earthquake
max
, corrected cone penetration resistance
q
c
1
(kg/cm
2
), or
Japanese standard penetration test
N
1
value. For practical purposes, assume the Japanese stan-
dard penetration test
N
1
value is equal to the (
N
1
)
60
value from Eq. (5.2). (
Reproduced from
Kramer 1996, originally developed by Ishihara and Yoshimine 1992.
)
assumed that the Japanese
N
1
value is approximately equivalent to the (
N
1
)
60
value calcu-
lated from Eq. (5.2) (Sec. 5.4.3).
3.
Volumetric strain:
In Fig. 7.1, enter the vertical axis with the factor of safety against
liquefaction, intersect the appropriate curve corresponding to the Japanese
N
1
value [assume
Japanese
N
1
(
N
1
)
60
from Eq. (5.2)], and then determine the volumetric strain
v
from the
horizontal axis. Note in Fig. 7.1 that each
N
1
curve can be extended straight downward to
obtain the volumetric strain for very low values of the factor of safety against liquefaction.
4.
Settlement:
The settlement of the soil is calculated as the volumetric strain,
expressed as a decimal, times the thickness of the liquefied soil layer.
