Environmental Engineering Reference
In-Depth Information
Table 1.
expected parameters values for the different volcanic materials.
Weathering
grade
spacing
dimensions
Unit weigth
[kn/m
3
]
σ
c,intact
[MPa]
e
intact
[GPa]
Description
RQD
Gsi
Fresh to slightly
weathered basalts
W
1-2
F
2-3
80-100
70-90
28-31
100-1000
50-100
Moderately weathered,
partially vacuolar basalts
W
2-3
F
3-4
40-80
55-75
25-28
10-100
10-75
highly weathered,
vacuolar basalts
W
3-4
F
4-5
10-50
40-60
23-25
1-10
1-6
Fresh to slightly weathered
breccias
W
2-3
F
3-4
30-90
45-75
-
8-60
5-65
Moderatelly weathered
partially vacuolar breccias
W
4-3
F
4-5
20-70
35-55
-
1-8
0.1-8
highly weathered, vacuolar
disaggregated breccias
W
5
-n/a
n/a
0-20
n/a
-
-
-
Breccious tuffs
W
4-5
-
30-90
n/a
-
0.5-7
0.1-2
Granular tuffs
n/a
n/a
n/a
-
1.5-10
0.2-1
silty-clayey or
clayey-silty tuffs
n/a
n/a
n/a
-
0.5-10
0.3-4
Figure 7.
Uniaxial compression tests results.
5.3
Geological strength index
Based on the experience gained from the geotech-
nical investigations and the design projects involv-
ing these formations, it was possible to define
ranges for Gsi typical values. The proposed values
for the different types of basalts and breccias are
presented in Figure 9. although most of tuffs are
transition materials between soft rocks and com-
pact residual soils and therefore the hoek-Brown
criterion should not be applied, this figure presents
some possible values of Gsi for tuffs.
1
0.9
0.8
0.7
0.6
0.569
0.5
0.4
0.367
0.3
0.2
Basalts
Breccias
0.1
0.076
0
0.1
1
10
100
1000
Uniaxial Compressive Strength [MPa]
5.4
Dilatometer results
only 8 dilatometer test results are available in com-
plex β
2
, 4 from basalts and other 4 from breccias.
Figure 8. cumulative frequencies of the uniaxial com-
pressive tests on basalts and breccias.
