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
* i
ndicates technique more likely
than others to be useful
4
Radon
as 1 above
L
1. pre-construction geological desk
study and risk assessmen
t*
2. monitoring of tunnel atmosphere for
signi
L
L
L
1. failure to identify radon
at elevated levels
2. long term affects on
workforce health
3. temporary evacuation of
drive during remedial
works
cant changes in character or
composition
3. provision of adequate ventilation
*
4. consider also hazard 3
5
Excessive volume
of groundwater
as 1 above
plus
permeable
strata
and fractured
ground
associated
with 1 above
H
1. hydrological testing in GI boreholes
*
2. pre-construction geological desk
study and risk assessment, tunnel
depth
*
3. probe drilling ahead of face through
control valve grouted into rock
ahead of TBM cutters and
monitoring of water volume and
pressure
*
4. packer testing to measure
permeability ahead of face
*
5. TSP to detect likely geological
structure
s*
6. monitoring of water make from face
and signi
M
H
H
1. failure of grouting
programme ground
freezing
2. underestimation of
inow
3. failure of EPBM
bulkhead
4. failure of pumps
5. temporary evacuation of
drive or
6. temporary loss of drive
cant changes in volume or
