Geology Reference
In-Depth Information
Initial void ratio:
The initial void ratio, e 0 , can be computed by dividing initial vol-
ume of void in the specimen, V v , by volume of solid in the speci-
men ( V s ). That is,
A
H 0
H s
e 0 V v
1
2
V s
AH s
or
H 0 H s
H s
(20-7)
e 0
[B] Time versus Deformation
1. From those increments of load where time-versus-deformation read-
ings are obtained, plot deformation readings versus logarithm of
time (in minutes) for each increment of load or pressure as the test
progresses and for any increments of rebound where time-versus-
deformation data have been obtained. See Figure 20-3.
2. Find the deformation representing 100% primary consolidation
(d 100 ) for each load increment. First, draw a straight line through
the points representing final readings that exhibit a straight-line
trend and flat slope. Then, draw a second straight line tangent to
the steepest part of the curve of deformation versus the logarithm
of time. The intersection of these two lines represents the defor-
mation corresponding to 100% primary consolidation. Compres-
sion that occurs subsequent to 100% primary consolidation is
defined as secondary compression. (See Figure 20-3.)
3. Find the deformation representing 0% primary consolidation (d 0 ) by
selecting deformations at any two times that have a ratio of 1:4. The
deformation corresponding to the larger of the two times should be
greater than one-fourth but less than one-half of the total change in
deformation for the load increment. The deformation corresponding to
0% primary consolidation is equal to the deformation corresponding
to the smaller time interval less the difference in the deformations for
the two selected times. (See Figure 20-3.)
4. The deformation corresponding to 50% primary consolidation (d 50 )
for each load increment is equal to the average of the deformations
corresponding to the 0 and 100% deformations. The time required for
50% consolidation under any load increment may be found graphi-
cally from the curve of deformation versus the logarithm of time for
that load increment by observing the time that corresponds to 50% of
the primary consolidation of the curve [1]. (See Figure 20-3.)
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