This manual answers the question why are bored
tunnels, particularly those excavated by microtunnelling and TBMs (tunnelling boring machines), in such high
demand in Asia at this time? Issues relating to the application of these techniques
are discussed frankly for the full range of geological conditions encountered in
Asia’s key cities. This is presented with the steps necessary to help ensure
their successful application - to realise the benefits and avoid the pitfalls.
Aspects of good site investigation practice are given and the advantages and disadvantages
of machine options in comparison with the use of traditional methods are outlined.
A collection of twenty five case histories are presented
illustrating different aspects of TBM performance with respect to the specific geological
conditions encountered on site. In many cases the delays encountered have been quantified
and key aspects of TBM design and the Contractors performance are critically
reviewed. These cases include microtunnelling, hard rock TBMs, machines for soft
ground and the new range of hybrid multi-mode TBMs for mixed fax condition. Methods
of predicting machine utilization rates, cutting rates and rates of progress are given.
A section on water inflow issues
affecting TBM performance in rock tunnels is included. A new empirical method of
predicting inflows is presented together with means of controlling water inflows
by pre-grouting techniques.
Finally contractual
issues arising from the use of so called ‘fixed price’ contracts, a risk sharing
option for rock tunnelling contracts, and an outline of the ‘Partnering’ value
added approach are discussed.
