Geology Reference
In-Depth Information
The British Tunnelling Society Joint Code of Practice for Risk
Management of Tunnel Works in the UK (BTS, 2003) was prepared
jointly by the Association of British Insurers and the BTS and sets out
requirements regarding risk assessment and management for any tunnel
with a contract price of more than £1 million. In effect, it is mandatory
in the sense that without its adoption, no insurance will be forthcoming
for an underground project. The Code of Practice sets out how and
when risk is to be assessed and managed, and by whom. Risks are to be
assessed at the project development stage (design), by the contractor at
tender stage and during construction through a risk register.
The Code also requires the ground reference conditions or geotech-
nical baseline conditions to form part of the contract, but as noted in
Chapters 2
and
4,
de
nition of such conditions is not always straight-
forward. Whilst the intention to avoid dispute is laudable, there may
be considerable dif
culty in summarising geological and geotechnical
conditions succinctly and unambiguously.
The ways that risk can be assessed at investigation and design stages
are illustrated by the example of the 16.2 km Young Dong rock tunnel
in Korea, as presented in Appendix E-1 and E-2. Given an appreciation
of the ground conditions along the route, based on a well-conducted
site investigation, the hazards associated with the various options for
construction can be considered. Once these have been identi
ed, their
likelihood and seriousness can be rated in terms of potential conse-
quence (e.g. programme, cost, health and safety) and methodologies
devised for mitigation prior or during construction. Decisions can then
be made on how to proceed.
During construction, hazards that were anticipated at the design stage
may prove real or illusory. New ones will be identi
ed and need to be
dealt with. The current way of so-doing is to employ a risk register in
which hazards are identi
ed and assigned to individuals in the project
team to derive strategies for their avoidance or mitigation. In the BTS
Code of Practice (2003), this is identi
ed as a task for the contractor
but the register will include risks brought forward from the project
development stage. In practice, it may well be the project engineer
rather than the contractor who manages the construction risk register,
perhaps at monthly meetings held to monitor progress on mitigating
each of the identi
ed risks, remove from the register those that have
been dealt with, and recognise and assign to individuals any new risks
identi
ed during the course of the work. Brown (1999) outlines the
risk management procedures adopted for the successfully completed
Channel Tunnel Rail Link Project in the United Kingdom, and a list of
