Geology Reference
In-Depth Information
Hazard
Possible mitigation measures prior to
and during construction to reduce
likelihood or consequence of hazard
Impact of
mitigation
measures and
risk
Summary of main
residual risks
Title
Example of
circumstances
Notes * indicates technique more likely
than others to be useful
5. geological mapping to detect
disturbed or distressed strata *
6. grouting ahead and below tunnel to
consolidate strata *
7. post construction microgravity
survey (gradiometry) along line of
tunnel to identify cavities and areas
of untreated ground or to con
rm
consolidation undertaken
satisfactoril y*
8. consider also likelihood of hazards:
1, 2, 5, 7, 8, 9, 10, 11 and 15
M
1. GI boreholes structural
interpretation
2. pre-construction geological desk
study and risk assessment
3. probe drilling ahead of face and
beneath tunnel to detect areas of
weak ground. Monitoring rates of
drilling and character of drill
cuttings *
4. identi
M
M
M
1. failure to identify ground
conditions
2. dif
14
Ground heave
proximity to
faults, shear
zones,
old mine
workings,
folded
ground and
places where
stress
conditions
atypical
culties in moving
TBM forward
3. difculties in placing
lining
4. delays in programme
5. incorrect lining selection
6. post construction lining
failure
7. increased maintenance
costs
cation of mining features
5. geological mapping to identify weak
or disturbed strata *
6. use copy cutters in weak ground to
increase tunnel diameter *
7. consider also likelihood of hazards: 15
 
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