A OPEN PIT MINING AÇIK OCAK MADENCİLİĞİ

3.5 SMR classification (Slope Mass
Rating)
The Slope Mass Rating (SMR) was
presented as a new geomechanical
classification for slopes in rock (Romana,
1985). The classification is obtained from
the RMR-system (Bieniawski, 1989), by
using an adjustment factor depending on the
relation between the slope and joints and
also a factor depending on excavation
method (Edelbro, 2003).
SMR = RMR basic + (F 1 . F 2 . F 3 ) + F 4
Where
F1 depends on parallelism between joints
and the strike of the slope face as:
F1 = (1-sin A)2,
Where A is the angle between the strike of
the slope face and strike of the joint.
F2 depends on the joint dip angle in the
planar modes of failure.
F3 refers to the relationship between the
slope face and joint dips (Bieniawski, 1976).
F4 is the adjustment factor depending on
excavation method of the slope.
The results of classification of rock mass
formations of Kef Essenoun is showing in
the following table:
Table 3. Classification of the rock
formations of Kef Essenoun (RMR system)
Properties Quaternary Limestone Phosphate Marl
Compressive
strength
2 7 4 2
Rock quality
designation 13 13 13 13
(RQD)
Spacing of
discontinuities
20 20 20 20
Condition of
discontinuities
10 10 10 10
Ground water
condition
15 15 15 15
RMR basic 60 65 62 60
Table 4. Classification of the rock
formations of Kef Essenoun (SMR system)
Properties Quaternary Limestone Phosphate Marl
F1 0.70 0.70 0.70 0.70
F2 0.15 0.15 0.15 0.15
F3 -25 -25 -25 -25
F4 -8 -8 -8 -8
(F 1 .F 2 .F 3 )+ F 4 -10.62 -10.62 -10.62 -10.62
SMR 49.37 54.37 51.37 49.37
SMR classes
(Romana,
1993)
Description: Class III; Normal
Stability: Partially stable
Failures: Planar failure in some joints and many
wedge failures
Support: Systematic
The results of SMR classification prove
that the mine was partially unstable and that
a plane failure will occur on the level of
some joints from where in this case the
failure occurred on the level of the bedding
plane separating the phosphate layer from
the marl layer.
Common for both soil and rock slopes is
the fact that the failure surface cannot
develop at the same instant throughout the
slope. There must be a progressive
mechanism of failure development
eventually leading to the full collapse of the
slope (Sjöberg, 1996).
3.6 Numerical Simulation
The Modeling is carried out by using the
finite element code for soil and rock
analyses PLAXIS. Calculations are carried
out in plane deformation, by using a model
of 300 m out of 500 m. The Mohr-Coulomb
elastoplastic constitutive law is selected.
This law offers the advantage of a low
number of parameters. The finite- element
model is illustrated in Figure 8.
Figure 8. The model geometry
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