Geology Reference
In-Depth Information
NO HAZARD
RISK
RISK
LEVEL
MITIGATION MEASURES
RESIDUAL
RISK LEVEL
LCR
L CR
3
Water ingress,
possibly under
high pressure up
to 40 bar (4 MPa)
Water in
cavities, joints
and
3
4
12
1. Tunnel drive to be
up-grade to allow water to
drain. (Not possible with
all drives.)
2. Provision of pumps to
cope with high
224
fissures in
the rock mass
entering
excavation
and causing
instability of
ground.
ows and
backup systems to deal
with pumps and power
failures.
3. Provision of probe drilling
to identify areas of high
water
Dif
culties
with shotcrete
application.
ows and to carry
out pre-injection grouting
to stem the
ow.
4. Excavation equipment
systems to be rated to IP68
or equivalent.
5. Use drainage channels to
control in
ows prior to
shotcreting.
4
Cavities in the
rock mass
(including mine
workings)
possibly
associated with
water in
Instability of
tunnel face,
roof fall and
side wall
instability.
3
4
12
1. Provision of TSP to
identify cavities in advance
of excavation.
2. Provision of probe drilling
to determine extent of
cavities and provide means
for grouting or other
advance stabilisation
measures.
3. Reduce length of
excavation advance.
236
Flooding.
ow
Need for
major
structural
work or
in
lling.
continued overleaf
