Geology Reference
In-Depth Information
¢ H
H 0
(21-1)
e
H is given by the deformation dial reading, provided that
the dial is set to zero initially.
As load is applied to the specimen, its cross-sectional area will in-
crease by a small amount. For each applied load, the cross-sectional
area A can be computed by the equation
The value of
Δ
A 0
1
(21-2)
A
e
where A 0 is the initial area of the specimen.
Each applied axial load P can be determined by multiplying the
proving ring dial reading by the proving ring calibration factor, and the
load per unit area can be computed by dividing the load by the corre-
sponding cross-sectional area.
The largest value of load per unit area or load per unit area at
15% strain, whichever is secured first, is taken to be the unconfined
compressive strength q u , and the cohesion c is taken to be half the
unconfined compressive strength.
[C] Graph
A graph of load per unit area (ordinate) versus unit strain (abscissa)
should be prepared. From this graph, the unconfined compressive
strength, q u , may be evaluated as either the maximum value of load per
unit area or the load per unit area at 15% strain, whichever occurs first.
[D] Sensitivity
If both the intact and remolded compressive strengths are measured,
determine the sensitivity, S T , as follows:
q u
1
intact specimen
2
(21-3)
S T
q u
remolded specimen
1
2
NUMERICAL
EXAMPLE
An unconfined compression test was performed in the laboratory, and
the following data were obtained:
[A] Specimen Data
Diameter of specimen, D 0
2.50 in.
Initial height of specimen, H 0
5.98 in.
Mass of specimen
991.50 g
Water content data:
Mass of wet soil plus can
383.41 g
Mass of dry soil plus can
326.78 g
Mass of can
50.56 g
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