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resulting from the period of maintaining the vertical stress constant varied from 5%
to 10% of the quasi-instantaneous initial settlement. Similarly, the effect of water on
grain crushing was pointed out by [LEE 67] as well as [CLE 81, MAR 77] and
others. They showed that the crushing of saturated particles required less stress than
it did for dry particles.
4.4.3.3.
Crushing of particles
For vertical stresses higher than 0.9 MPa, the increase in compressibility of the
granular skeleton of waste rock, as shown by the oedometric tests, is related to the
particle crushing phenomenon. Several authors have held this phenomenon
responsible for the contracting behavior observed.
Thus, the high pressures induced by the very weight of the materials stockpiled
in waste rock dumps with heights over 100 m generate significant particle crushing,
modifying the initial grain size distribution of the material and leading to an increase
in the amount of sands and fines in the granular matrix. This situation modifies the
void ratio and, consequently, the density and permeability.
ROM WR, loading
ROM WR, max. load
0.5
e
0.5
e
0.5
e
ROM WR, saturation under load
c
r
= 0.09
σ
pc
'=0.8 MPa
0.4
0.4
0.4
C
c
= 0.15
0.3
0.3
0.3
d
60
/
d
10
= 13
d
6
0
/
d
10
= 1
6
0.2
0.2
0.2
d
60
/
d
10
d
60
d
10
initial= 9
= 25
0.1
0.1
0.1
0.1
1
10 100
σ
v
'
(
0.1
x
MPa
)
0.1
1
10 100
σ
v
'
(0.1
x
MPa)
0.1
1
10 100
σ
v
'
(
0.1
x
MPa
)
0.5
e
0.5
e
0.5
e
Leached WR, saturation under load
Leached WR, loading
Leached
WR, max. load
c
r
= 0.035
σ
pc
'= 0.9 MPa
0.4
0.4
0.4
C
c
= 0.19
0.3
0.3
0.3
d
60
/
d
1
0
=
3
2
d
6
0
/
d
10
=
4
1
0.2
0.2
0.2
d
60
d
10
initial= 16
d
60
/
d
10
= 53
0.1
0.1
0.1
0.1
1
10
100
σ
v
'
(0.1
x
MPa)
0.1
1
10
100
σ
v
'
(0.1
x
MPa)
0.1
1
10
100
σ
v
'
(0.1
x
MPa)
Figure 4.4.
Large scale oedometric test results. ROM and leached waste rock (WR)
with initial homothetic grain size distributions
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