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Tunnel Induced Deformation using Modern Tunneling Equipment
A significant risk in
urban transportation tunneling is building, utility and other structural
damage caused by tunneling-induced deformation. Considerable effort, time
and cost is expended to account for and to mitigate the effects of tunneling-induced deformation. Conservative values of
volume loss, e.g., 0.5 to 1.0%, are used in preliminary building
assessment to identify structures requiring fortification or protection.
Numerous buildings are either strengthened or ground improvement efforts
are taken to protect them, e.g., compensation grouting. Both efforts are
costly and time-consuming. If such efforts were not required, tunneling
cost and risk could decrease significantly.
Tunneling practice in
North America and worldwide over the past decade has shown that tunneling-induced
ground deformation has decreased significantly. This is largely the result
of pressurized face tunnel boring machine (TBM) tunneling and their proper operation. Volume loss
on the order of 0 – 0.3% are increasingly common. The tunneling industry
therefore operates in an environment where large volume losses (0.5-1.0%)
are often planned for yet much lower values are realized (0-0.3%). The
goal of ‘negligible-deformation’ TBM tunneling is arguably within reach.
To realize this goal, the
community needs to better understand TBM tunneling-induced deformation
control. It is well understood that inadequate face pressure, the shield
annulus and the tail shield/segment gap are the general contributors to
ground and building deformation. However, there are many important
questions about these. Further, changes in geology and hydrogeology often
are the cause of deformation. Improved understanding of how TBM pressures
can mitigate these effects is needed.
and analyze, for a variety of North American tunneling projects completed
over the past 10-15 years, observed ground and building deformation as a
function of face, shield annulus and grout pressures, as well as geology
and geometry (diameter, depth, etc.).
and document the cause and effect relationship between these TBM-induced
pressures and the observed deformations. Convey deformation levels (as a
function of TBM-induced pressures and in different geology) in a
probabilistic fashion. Use
computational modeling with GDR information and TBM parameters to support
risk-based criteria for TBM operation (required pressures) that control
deformation (but that also does not slow production).
Better control of TBM
Less building fortification, less
ground improvement = lower cost.
A detailed literature search will
be conducted in order to obtain available information in regard to addressing
this specific problem. Literature
searches will include national technical reports, state DOT libraries and
personnel queries, university research programs, and association work.
|Sponsoring Committee:||AKB60, Tunnels and Underground Structures
|Research Period:||24 - 36 months|
|RNS Developer:||Mike Mooney|
|Source Info:||Committee members and friends|
|Index Terms:||Tunnel borers, Tunneling, Tunnels, Deformation, |
Bridges and other structures
Vehicles and Equipment
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