Geology Reference
In-Depth Information
Figure 5.26
Patchily in
lled
sheeting joints
following
intermittent
to failure. Details
are given in
Hencher (2006).
Approximately 25 mm
sub-vertical
displacement of joint
Minor seepage noted on
sheeting joint on
24.10.2000, four days
after a heavy
rainstorm
General direction
of downslope
movement
20 mm thick
clay infill - soft to firm light brown
clay with occasional sand grains
Clay infill
Rock on rock
Clay infill
Rock on
rock
Approximately 5 mm
sub-horizontal
displacement of sheeting
joint. (Note trailing
corner has fractured)
0 0.1 0.2
m
Approximate Scale
component is then added to account for roughness using a Joint
Roughness Coef
cient (JRC) usually judged from standard pro
les
and ranging from 0 to 20. This can be dif
cult in practice (Beer et al.,
2002). JRC is then adjusted for the strength of the rock asperities vs.
stress conditions and for scale. Details are given in Brady & Brown
(2004) and Wyllie & Mah (2004).The criterion can be incorporated
within numerical software for modelling rockmass behaviour such as
UDEC (Itasca, 2004). The contribution to shear strength from small-
scale roughness is measured or estimated from standard shape pro-
cult in
practice (Beer et al., 2002). Larger-scale roughness (waviness) then
must be accounted for, over and above JRC, and scale corrections
applied.
An important point that needs to be emphasised is that dilation-
corrected basic friction parameters from direct shear tests on natural
files (Joint Roughness Coef
cient), although this can be dif
