Seismic Design of Tunnels - Parsons Brinckerhoff

6.0 SUMMARY
A rational and consistent methodology for seismic design of lined transportation
tunnels was developed in this study which was mainly focused on the interaction between
the ground and the buried structures during earthquakes. Although transportation tunnels
were emphasized, the methods and results presented here would also be largely
applicable to other underground facilities with similar characteristics, such as water
tunnels, large diameter pipelines, culverts, and tunnels and shafts for nuclear waste
repositories (Richardson, St. John and Schmidt, 1989).
Vulnerability of Tunnel Structures
Tunnel structures have fared more favorably than surface structures in past
earthquakes. Some severe damages — including collapse — have been reported for
tunnel structures, however, during earthquakes. Most of the heavier damages occurred
when:
• The peak ground acceleration was greater than 0.5 g
• The earthquake magnitude was greater than 7.0
• The epicentral distance was within 25 km.
• The tunnel was embedded in weak soil
• The tunnel lining was lacking in moment resisting capacity
• The tunnel was embedded in or across an unstable ground including a ruptured fault
plane
Seismic Design Philosophy
State-of-the-art design criteria are recommended for transportation tunnel design for
the following two levels of seismic events:
• The small probability event, Maximum Design Earthquake (MDE), is aimed at public
life safety.
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