Environmental Engineering Reference
In-Depth Information
The same comparison has been carried out with
the
Sch-do
unit. The Gsi values estimated as esti-
mated from the borehole logs have been superim-
posed on those proposed by hoek and Marinos
for the same type of rocks. The results are shown
in Figure 12, where similar conclusions can be
derived of the good agreement in general of both
sets of data.
Sh UCT
70%
60%
50%
40%
30%
20%
10%
0%
MPa
4
Rock Mass DeFoRMaBiliTY
MoDUli
Figure 11. Frequency histogram of the Ucs and PlT
compressive strength test results in the sh unit.
The following table summarizes the values
obtained from the laboratory tests of intact rock
and the estimation and assessment of Gsi, RMR,
mi and other geomechanic parameters of the geo-
logical and geotechnical units identified along the
tunnel.
Bieniawski proposed a simple correlation based
upon RMR, after exhaustive in situ deformability
tests planes in three projects, the orange River
Water Project (a dam founded in volcanic rocks
and a tunnel excavated in shales), the Drakensberg
scheme (an hydroelectric central in a horizon-
tal strata of layers of shales and sandstones) and
the elandsberg scheme (another hydroelectric
central):
Sh RQD
35%
30%
25%
20%
15%
10%
5%
0%
RQD (%)
Figure 12. Frequency histogram of the RQD index in
borehole columns corresponding to the sh geological
unit.
- For RMR > 50 the deformation modulus can be
expressed by a linear equation:
e rm = 2 RMR-100 (GPa)
- later
studies
recommended
its
use
when
55 < RMR < 90.
UNIDAD GEOTÉCNICA
Sh(lutitas-chert)
GSI
25 -42 /35
20
46
For RMR < 55 the Bieniawski equation can't
be used. There are subsequent investigation works
that try to find connections between erm and the
RMR < 50, like the serafim and Pereira (1983)
equation, deduced from various in situ deforma-
tion tests in several dams in asia:
Falla
46
13
7
23
2
2
3.Schistoseserpentinite.Schistositymaybemoreorlesspronouncedand
theirplanesaltered.
46
25
41
3
2
5
2
2
e rm = 10
(RMR-10/40)
(GPa)
4.Poortoverypoorqualityshearedserpentinite.Thefragmentsarealso
consistingfromweakmaterials
Figure 13. Display of the Gsi assessments for the
B2o-1 to B2o-8 boreholes corresponding to the sh and
Fault geotechnical units compared with the proposed
range for serpentinites rocks with a marked schistosity
and very low to low geomechanics quality ophiolite com-
plex of orthys by hoek and Marinos.
The RQD is generally low, ranging between 0%
Finally, in figure 13 it is shown a comparison
of these values of Gsi with the ones proposed by
hoek and Marinos (2001).
1. Boreholes B2o-3, B2o-4 and B2o-5.
2. Boreholes B2o-6 and B2o-7.
