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Table 12. Relative severity ratings in transportation tunnels.
Relative
Low High
Severity
Immersed Tube
Cut-and-Cover
Construction
Type Soft Ground Tunnel
Rock Tunnel
Underwater
Running and Flowing
Cohesive Running
Fast Raveling
Ground Type
Firm to Raveling
Highly Jointed / Weathered Rock
Moderately Jointed Rock
Massive Rock
Rock Bolts / Dowels
Shotcrete
Steel Ribs and Lattice Girder
Support Type
Unreinforced Concrete
Reinforced Concrete
Steel Backfilled with Concrete
Near Surface
Tunnel Depth Shallow
Intermediate
Deep
transport the payload and consolidating at a critical loca- delivery device, and ultimate target. The right side of the tables
tion inside the tunnel. contain each of the major tunnel types: immersed tube, cut-
· Introduction of very large IEDs, which are delivered by and-cover, bored or mined in soft to firm ground, bored or
ship, barge, or boat. The depth charge is dropped and det- mined in strong rock, and air-rights structure tunnels. Each
onated above an immersed tube tunnel. row represents a unique hazard or threat scenario. If that sce-
· Fire load larger than 341 MBTU per hour (100 MW). nario poses danger to a certain type of tunnel, then that inter-
secting cell describes the physical vulnerability (PV), the
In addition to the size of the hazard or threat, other critical operational vulnerability (OV) and the damage potential (DP).
factors considered in the damage potential rating included type The damage potential is presented in terms of the rating abbre-
of tunnel construction, ground condition, ground support sys- viations given in Table 13 (from A to F).
tem, and soil or rock overburden thickness. The damage poten-
tial rating is divided into six categories--letters A through
F--ranging from severely catastrophic (A) to negligible (F). 4.4.6 Summary
Tables 14, 15, and 16 present structural vulnerabilities to the The information presented in Section 4.4 allows tunnel
most likely hazard or threat scenarios for road tunnels, transit facility owners, operators, and engineers to conduct prelimi-
tunnels, and rail tunnels, respectively. These tables basically nary vulnerability rating assessments of their facilities and, if
combine the information given in Table 3 (hazard and threat needed, to derive priority lists of tunnel structural compo-
scenarios) with the information given in Table 13 (damage nents for further study.
potential ratings for transportation tunnels). The hazard and
threat scenarios have been rearranged into subtables based on
the "Path to Target" and the "Target." These items are located at 4.5 System Elements and
the top left side of each subtable. The hazards and threats pre- Vulnerabilities
sented on the left side of the tables include very large, large,
4.5.1 Key Safety Functions
medium, and small IEDs and large fires. All of the hazards and
threats were developed further to identify hazard and threat There are many systems serving transportation tunnels. Of
scenarios that include hazard and threat, path to target, tactical these systems, many are not visible but are nonetheless
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Table 13. Damage potential ratings for transportation tunnels.
Fire (>34
Soil or Rock Explosion
Tunnel MBTU per
Ground Support System Overburden
Type 1 hour, or
Thickness Small Medium2 Large3 100 MW)
Strong < 1 x diameter E D C D
All Types
Rock > 1 x diameter E D C D
Rock Bolts with Wire < 1 x diameter D B B B
Mesh/Lattice Girder/
Shotcrete > 1 x diameter D B B B
Steel Ribs with or < 1 x diameter F B B B
Soft Rock/ without Liner Plate >1 x diameter F B B B
Firm
Bored or Mined
Ground Cast-in-Place < 1 x diameter F B B C/B
Concrete Liner > 1 x diameter F C/B B C/B
< 1 x diameter D B A B
Segmental Concrete
> 1 x diameter D B B/A B
Steel Ribs or Lattice < 1 x diameter D B A B
Girder with Shotcrete >1 x diameter D B A B
Loose/Soft Cast-in-Place < 1 x diameter F B A C/B
Ground Concrete > 1 x diameter F C/B B/A C/B
< 1 x diameter D B A B
Segmental Concrete
> 1 x diameter D B A B
Unreinforced < 15' D B A C
Concrete/Masonry
Firm Lining > 15' D B A C
Ground < 15' D B A C
Cut-and-Cover
Reinforced Concrete
Lining > 15' D B A C
Unreinforced < 15' D B A C
Concrete/Masonry
Loose/Soft Lining > 15' D B A C
Ground < 15' D B A C
Reinforced Concrete
Lining > 15' D B A C
Steel Tube D B A D
Immersed Tube
Concrete Tube D B A D
Air-Rights Structure D C B D
Notes:
1. Transported by foot.
2. Transported by car.
3. Transported by truck.
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