Environmental Engineering Reference
In-Depth Information
500
400
300
Rebound curves
200
Compression curve
100
P
i
P
f
P
l
0
0
5
10
15
Corrected pressure, in bars
20
25
30
35
FIGURE 3.87
Typical pressuremeter test results. (From Dixon, S. J.,
Determination of the In Situ Modulus of Deformation of Rock.
ASTM Special Technical Publication 477, American Society for Testing and Materials, Philadelphia, PA, 1970.
Copyright ASTM International. Reprinted with permission.)
ume over length of cell (790 cm
3
for NX hole), and
V
m
the fluid volume injected into cell
for the average applied pressure.
K
2700 cm
3
typically, for an NX hole and
ν
0.33.
Moduli and Strength Parameters
Estimating Young's modulus E from E
c
:
Menard (1965) suggests the use of a “rheological”
factor
α
to convert the compression modulus into Young's modulus, expressed as:
E
E
c
/
α
(3.76)
Menard's values for
found to be related to the amount of precompression in the material. There is some con-
troversy over the selection of the
α
α
factor (Silver et al., 1976), but most practitioners appear
to use Menard's values.
Data Applications:
Estimating values for deformation modulus
E
c
.
●
Estimating the undrained shear strength from the expression (Menard, 1975)
●
s
u
(
P
L
P
o
)/2
K
b
(3.77)
where
P
L
is the limiting pressure,
P
o
the at-rest horizontal stress
K
o
and
K
b
the coefficient varying with
E
c
/
P
L
, typically 5.5 (Lukas and deBussy, 1976).
σ
v
Estimating allowable bearing value for foundations (CGS, 1978).
●
