Geology Reference
In-Depth Information
(continued)
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
11
Variable face
conditions
karst boulder
beds and
cave/mine
working
in
M
1. GI boreholes
2. pre-construction geological desk
study and risk assessment
3. probe drilling ahead of face through
TBM head and monitoring rates of
drilling and character of drill
cutting
s*
4. geological mapping to detect changes
in structur
e*
5. TSP to detect likely geological
structures which could be associated
with variable face conditions
6. ground probing radar to detect clay
or high densities of fractures
7. use TBM face with ability to deal
with small amounts of soft material
(tunnel alignment may be
compromised
*)
8. consider also likelihood of hazards:
2, 3, 5, 6, 7, 8, 9, 10, 11, 16 and 17
M
L
M
1. failure to anticipate
conditions
2. damage to cutters
3. stability problems and
damage to cutter head
4. delays to programme
5. increased risk of water or
gas inrush
ll,
fault zones
and
highly folded/
disturbed
areas
