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
10. grouting ahead of tunnel face
*
11. consider also likelihood of hazards: 2,
3, 5, 6, 7, 8, 9, 10, 11, 16 and 17
2
Inrush of
as 1 above
M
1. GI boreholes
2. pre-construction geological desk
study and risk assessment
*
3. probe drilling ahead of and around
the face through TBM head.
Monitoring of character of
L
L
L
1. failure to identify
presence of gas
2. explosion during probe
drilling because of
ammable gas
ush
failure at the drill bit
3. escape of gas and
explosion in the driveage
4. injury to workforce
5. temporary evacuation of
drive during remedial
works or
6. temporary loss of drive
ush
cant changes in character or
composition
*
5. inspection of probe drill cuttings to
identify weak or unconsolidated
material, monitoring of strata colour
and odour for unanticipated change
s*
6. TSP to detect likely geological
structures
*
7. monitoring of tunnel atmosphere for
signi
cant changes in character or
composition
*
8. GPR to detect cavities, clay or high
density of fractures
9. geological mapping to detect changes
in structure, strata distress
