Environmental Engineering Reference
In-Depth Information
s
parameters are more important for rock mass
of medium quality than good quality. Reduc-
tion of
m
r
and
s
r
parameters less than
2
3
m
p
and
3
s
p
causes more deformation in the rock mass,
therefore it should be managed to retain
m
r
and
s
r
parameters more than
3
m
p
and
3
s
p
by means
of controlled blasting or mechanical excavation.
• according to above mentioned results, it is con-
cluded that the method of excavation should
be designed so that it causes the least reduction
in strength parameters of rock mass first for
medium quality (often with elastic-strain soften-
ing behavior) and in the second order for good
quality of rock masses (often with elastic-brittle-
plastic behavior).
2
Figure 4. effect of variation of
c
r
(a) and
ϕ
r
(b) param-
eters on GRc for data set 1-1.
it shows that sensitivity of rock mass deformation
decreases in terms of variation of the
c
r
parameter
with increasing rock mass strength.
in the next stage it was managed to change
parameter
ϕ
r
into
ϕ
ReFeRences
alonso, e., alejano, l.R., Varas, F., Fdez-Manin, G.,
carranza-Torres, c., 2003. Ground response curves
for rock masses exhibiting strainsoftening behavior.
Int. J. Numer. Anal. Meth. Geomech.
27, 1153-1185.
Brady, B.h.G., Brown, e.T., 1993.
Rock Mechanics for
Underground Mining
. chapman & hall.
Brown, e.T., Bray, J.W., ladanyi, B., hoek, e., 1983.
Ground response curves for rock tunnels.
J. Geotech.
Eng. ASCE
109, 15-39.
carranza-Torres, c., Fairhurst, c., 1999. The elasto-
plastic response of underground excavations in rock
masses that satisfy the hoek-brown failure criterion.
Int. J. Rock Mech. Min. sci.
36, 777-809.
Detournay, e., 1986. elastoplastic model of a deep tun-
nel for a rock with variable dilatancy.
Rock Mech.
Rock Eng.
19, 99-108.
Duncan Fama, M.e., Trueman, R., craig, M.s., 1995.
Two and three dimensional elasto-plastic analysis for
coal pillar design and its application to highwall min-
ing.
Int. J. Rock Mech. Min. sci. & Geomech. Abstract.
32, 215-225.
Florence, a.l., schwer, l.e., 1978. axisymmetric com-
pression of a Mohr- coulomb medium around a cir-
cular hole.
Int. J. Number. Anal. Meth. Geomech.
2,
367-379.
Guan, Z., Jiang, Y., Tanabasi, Y., 2007. Ground reaction
analyses in conventional tunneling excavation.
Tunnel.
Under. space Technol.
22, 230-237.
hoek, e., Brown, e.T., 1980. Underground excavation in
rock.
Institution of Mining and Metallurgy
, london.
kargar, a.R., Rahmanejd, R., 2009. The effect of vari-
ous constitutive models on ground response curve.
M.Sc. Thesis
, Bahonar University of kerman.
lee, Y.-k., Pietruszczak, s., 2008. a new numerical pro-
cedure for elasto-plastic analysis of a circular opening
excavated in a strain-softening rock mass.
Tunnelling
and Underground Space Technology
23 (2008) 588-599.
Park, k.-h., Tontavanich, B., lee, J.-G., 2007. a simple
procedure for ground response curve of circular tunnel
in elastic-strain softening rock masses.
Tunnelling and
Underground Space Technology
23 (2008) 151-159.
3
,
and
ϕ
p
. it is observed
from figure 4b that increasing
ϕ
r
parameter causes
a reduction in rock mass deformation for data set
1-1. Table 2 shows the same procedure for data set
1-2 and 2. it can be inferred by comparing these
three set of data that relative displacement of rock
mass decreases vs. variation of parameter
ϕ
r
from
data set 1-1 to 2 based on table 2. in other word,
relative rock mass displacement reduces in term of
variation of
ϕ
r
parameter with increasing strength
of rock mass. it is also observed that increment
of
ϕ
r
and
c
r
parameters cause a reduction in rock
mass deformation. however these variations are
more intense for low values of
ϕ
r
and
c
r
.
it can be concluded from table 2 that rock mass
deformation is more sensitive to the variation of
Mohr-coulomb parameters than hoek-Brown ones.
p
2
3
ϕ
p
4
conclUsion
• By comparison of the relative displacement
caused by changing strength parameters in
hoek-Brown and Mohr-coulomb criteria, it
can be concluded that the sensitivity of rock
mass deformation is higher for Mohr-coulomb
criterion than hoek-Brown in respect of varia-
tion of strength parameters.
• it is inferred from analyses that with improving
rock mass quality, the sensitivity of rock mass
deformation reduces in resp
ec
t of strength param-
eter variation for Mohr-coulomb criterion.
• it is observed from table 2 that variation of rock
mass strength parameters causes more relative
deformation for elastic-strain softening rock
mass than elastic-brittle-plastic. Therefore
m
and
