Geology Reference
In-Depth Information
(L = likelihood, C = consequence, R = L × C = risk). Residual risk is likely outcome after application of
mitigation measures.
NO HAZARD
RISK
RISK
LEVEL
MITIGATION MEASURES
RESIDUAL
RISK LEVEL
LCR
L CR
Ravelling
ground, roof
falls and
sidewall
and/or face
instability
with high
amount of
primary
support.
1
Highly jointed
rock mass
(possibly in
association with
high-pressure
water).
See Hazard 3 for
water ingress
speci
3
4
12
1. Reduce length of
excavation advance; face
support and/or buttressing
and/or partial face
advance.
2. Reduce powder factor to
lessen blast damage.
3. Increase rock support and
install rock support in the
form of rock bolts and steel
224
cally.
fibre reinforced shotcrete
without delay.
4. Probing and pre-injection.
2
Fault zones
Soft ground or
mixed face
conditions
with potential
roof falls and
sidewalls
instability
requiring a
high degree of
primary
support.
3
4
12
1. Reduce length of
excavation advance; face
support and/or buttressing
and/or partial face
advance.
2. Reduce powder factor.
3. Increase rock support and
install rock bolts, steel
326
fibre reinforced shotcrete,
lattice girders and spilling
bars without delay.
4. Provision of probe drilling
to identify these features
ahead of the excavation
face.
5. Provision of Tunnel
Seismic Prediction (TSP) to
identify fault zones ahead
of the excavation face.
6. Provision of
instrumentation to
monitor movement to
optimise support.
