3485
Technical Committee CFMS /
Comité technique CFMS
Fig.5 The P-S curve of 1# footing(3.0m×3.0m)
Fig.6 The P-S curve of 3# footing(3.0m×3.0m)
From the predictions of the above two methods, they all
get good results. For homogeneous foundation formed by only
one category of soil, the two methods result in the same effect,
but as to the non-homogeneous layered soil expressed directly
by hyperbolic curve, when the small-size plate loading test
results are used for the large-size foundation, its reflection of
the deep soil is not enough.
When using the second method to calculate the layered
foundation settlement by the tangent modulus method, it can
adopt different c and φ for different soil layers, as well as the
initial tangent modulus
0
t
of soil to reflect the effect on the
deep soil and the soil of different layers, which has better
adaptability for the foundation generally composed by the
multi-layer soil.
E
The parameters of different test points inversely
calculated by the tangent modulus method are shown in Table 2.
Table 2. Foundation soil parameters of 5 plates inversely
calculated by loading test data
Plate loading
test Number
0
t
MPa
E
/
u
/kPa
p
c
/
kPa
/°
5#(1.0m×1.0m)
83.4
1399
0
37.2
2#(1.5m×1.5m)
84.4
1202
0
35.5
4#(2.5m×2.5m)
84.7
1340
0
34.8
1#(3.0m×3.0m)
90.9
1405
0
37.0
3#(3.0m×3.0m)
86.4
1128
0
35.6
The average of soil parameters in Table 2 are as
follows:E
to
=86Mpa,φ=36
°
. The settlement load curve of each
plate calculated by taking these soil parameters and using
tangent modulus method is shown in Figures 7 to 11.
The figures show that the calculation and test results are
in consistent to a large extent. But the accuracy is less than that
of Figures 2 to 6. This is mainly because the soil parameters in
Figures 2 to 6 are inversely calculated by each pilot point, while
Figures 7 to 11 are calculated by using the average value of
inversely calculated parameters at each test point. In actual
engineering, this heterogeneity makes it unlikely to conduct
plate loading test for each foundation location. Therefore, this
paper further explores the use of easier pressuremeter test to
determine the initial tangent modulus
to
E
of tangent modulus
method in the soil at different depth by using static cone
penetration test (CPT) to determine the angle of internal
friction
in the tangent modulus method in sand of different
layers. And c = 0.
Fig.7 5#footing(1.0m×1.0m)Fig.8 2#footing(1.5m×1.5m)
Fig.9 4#footing(2.5m×2.5m)Fig.10 1#footing(3.0m×3.0m)
Fig.11 3#footing(3.0m×3.0m)
1.3
The initial tangent modulus of soil layer determined by
ssuremeter test
The formulation of the initial tangent modulus can be
determ by the curve of pressuremeter test:
pre
ined
m
l
E
f
l
m
l
t
p p
E
p p
E
)
)
)
(
0
0
(6)
int
p
0
, p
1
),
cal
e pressure
, limit pressure
the
odulus
be po
at the abov
el indicator. If the sand foundati
recognized as isotropic media, then the above calculation results
can be as the vertical indicators in settlement calculation.
According to the typical pressuremeter test curve (PMT-2,
the s
f
l
p p p p
( )
(
0
0
p p
(
)
(
0
The initial tangent modulus of foundation
to
E
can be
determined by using the corresponding loading erval (
l
p
and
e calculated tangent
criti edg
It should
used
f
p
m
E
.
out th
pressuremeter m
inted
modulus is the lev
on is
tandard method of test execution standard
[8]
) on loading
test sites in Riverside Campus, Texas A & M
University,
l
kP
p
400
a
,
a
f
kP
p
280
,
a
kP p
20
0
.
After substituting in to the above formula, it can get:
m
m
t
E E
E
2.3
) 280
400 (
)20 400 (
0
(7)
1.4
Foundation strength parameters determined by static
cone penetration test
In the process of static cone penetration test (CPT), the
foundation soil strength failure occurs. The test data can vividly
