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
15
Squeezing ground
as 14 above
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
cutting
s*
4. identi
M
M
M
1. failure to identify ground
conditions
2. difculties in moving
TBM forward
3. dif
culties in placing
lining
4. delays in programme
5. incorrect lining selection
6. post construction failure
of tunnel lining
7. increased maintenance
costs
cation of mining features
5. geological mapping to identify weak
or disturbed strata
*
6. use of copy cutters in weak ground to
increase tunnel diamete
r*
7. consider also likelihood of hazards: 14
16
Shock loading of
tunnel lining
collapse of
karst, old
mine
workings
above,
below or
adjacent to
tunnel lining.
Earthquake,
fault rupture
H
1. GI boreholes proving of extensive
karst features or open mine workings
2. pre-construction geological desk
study and risk assessmen
t*
3. seismic hazard assessment
4. detection of cavities >> tunnel
diameter from probe drilling ahead
of and around the face through TBM
hea
d*
5. TSP to detect cavities in vicinity of
tunnel bore
*
L
H
H
1. failure to detect cavities
2. failure of grouting
programme
3. inability to grout
workings due to depth
topography
4. tunnel collapse and
temporary loss of drive
5. selection of incorrect
tunnel lining
continued overleaf
