Environmental Engineering Reference
In-Depth Information
grains and to the need of an increase of the volume
of the specimens to provide the shear failure.
The values of friction angle obtained in the
consolidated drained direct shear tests, with the
fractions passed through the 2.00 mm sieve and
through the 4.75 mm sieve are similar, while the
obtained values for the cohesion show a wide
The consolidated drained direct shear tests
results on the two entire samples led to higher
values, both in friction angles and cohesion, when
compared to previous results, which are obviously
related to the bigger dimensions of the particles
and the correspondent increase volume during the
shear failure phase.
Figure 2 shows an example of a test made with
the entire grading on the big shear box.
compaction and cBR tests were also performed,
and values for the maximum dry density were
obtained between 13.5 and 17.1 kn/m
3
, for the
optimum water content values between 4.5 and
17.7%. For the cBR the values varied between 40
and 96%.
seven in situ plate load tests were performed
with a 0.6 m diameter plate. in these tests a wide
dispersion in the values of the deformability secant
modulus was obtained, which varied between 10 and
250 MPa, for a tension of 300 kPa.
The values of the deformability modulus
obtained in situ are closer to the values obtained
in the laboratory tests, presented by serrano et al.
(2007), and are more different from the values
presented by Uriel & serrano (1976,
in
serrano
et al., 2007), which were obtained with in situ plate
load tests, using a 1 × 1 m
2
plate.
500
3.1.2
Azores samples
Tests for grain size distribution, specific weight
determination,
400
cBR
and
los
angeles
were
300
performed in laboratory on these materials.
Particle size distribution results are presented
in Figure 5, being possible to see that they are
mainly well graduated gravel. on what concerns
the particle specific weight, the values are between
19.6 and 21.6 kn/m
3
, and the water absorption
range between 3.3 and 14.8%
Results from los angeles on the 18 samples
tested are presented in Figure 3, showing a high
variation of values, between 25% to 70%.
according to Fraga (1988) the coefficient of los
angeles in these materials varies with the fraction
of material that is tested. That researcher found
that the same material had a value of los angeles
coefficient that was lower when tested in the finer
fractions and higher in the coarser fractions. he
also found that this variation was linearly with the
fineness modulus. The behaviour of this material
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
Figure 1. Results obtained with the consolidated
drained direct shear tests on Madeira samples.
200
180
160
140
120
100
80
150 kPa
100 kPa
75 kPa
50 kPa
60
90
40
20
80
0
70
0
20
40
60
80
8
60
50
6
40
4
30
Red
Black
Red - Fraga (1988)
Black - Fraga (1988)
2
20
0
10
0
20
40
60
80
0
-2
5(D)
5,5
6(C)
6,5
7(B)
(A)
8(G)
(F) 9(E)
Horizontal displacement (mm)
Fineness modulus (Test Fraction)
Figure 2. example of a test made with the entire
grading in the big shear box.
Figure 3.
los angeles tests done in azorean samples.
