Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
27 Every tunnel is unique. This chapter shows how complex tunnels can be. Considering the significant cost of tunnel construction, there is a reasonable attempt to use tunnels for different purposes. The combined-use road tunnels can be classified as follows: ⢠Combined use for road vehicles and pedestrians and bicycle riders. ⢠Combined use for road vehicles and utilities, including gas fuel and electrical power lines. ⢠Combined use for road and railway vehicles. ⢠Railway tunnels with railway cars that carry road vehicles. A channel tunnel is an example. This type of tunnel is considered a railway tunnel and is not covered by this report. COMBINED USE FOR ROAD VEHICLES AND PEDESTRIANS Tunnels for combined use can be classified as follows: ⢠Tunnels with pedestrian walkways and bicycle lanes. The Stockton Street Tunnel in San Francisco is an example of this type of tunnel (see Figure 5). Most of these tunnels are relatively short. Such tunnels require special attention for air quality and security. Some road tunnels allow for animals to pass through under supervision. ⢠Tunnels that accommodate bus stops (see Figure 6). Passengers occupy the Stop area only and do not travel along the tunnel. This bus tunnel in Seattle is an exam- ple. Since 2009, a downtown Seattle Transit Tunnel has allowed bus and rail. There are many regular road tun- nels that allow for any traffic and accommodate bus stops leading to the outside. Those tunnels may require special attention to public safety as they are similar to railway and metro tunnels dealing with higher concen- trations of people in the tunnel. However, this could be more dangerous from a fire standpoint owing to the pos- sibility of truck fires. COMBINED USE FOR ROAD VEHICLES AND UTILITIES Combined tunnels for road vehicles and utilities can include gas and fuel lines. These types of tunnels cross rivers and connect islands and even possibly continents. When finished, the Bering Straight Tunnel will contain a highway, railway, oil pipelines, and fiber optic cables. The installation of oil pipelines could lead to additional risk that would need to be addressed when designing for a fire. COMBINED USE FOR ROAD AND RAILWAY VEHICLES There are many examples of combined use for road and rail- way vehicles in tunnels (see Figure 7). Some tunnels have separate tubes for road traffic and separated tubes for railway traffic. Some of them have a single tube that serves for both road and railway traffic. An example of this is the Whittier Tunnel in Alaska. This 4-km (2.5-mile)-long, one-lane tunnel was designed as a combination highway and railway tunnel that allows cars and trains to take turns traversing the tunnel. It is the longest combined railâhighway use tunnel in North America. Drogden Tunnel between Copenhagen in Denmark and Malmo in Sweden is an example of the combined-use tunnel with separate tubes for road and railway vehicles (24). It is an immersed tunnel approximately 4 km (2.5 miles) long. Com- pleted in 2000, it consists of two uni-directional rail tunnels and two uni-directional road tunnels. All four tunnels are parallel. Between the two road tunnels there is a very narrow tunnel, or âcentral gallery,â which runs the length of the tunnels. The central gallery consists of three smaller âgalleries,â one on top of the other. At the top is a âservice gallery,â below that is an âescape gallery,â and below that is a small gallery for fire mains and drainage pipes (see Figure 8). There are cross-passages between the road tunnels and the narrow tunnel. Incidents occurred in these links in 2000, 2001, 2004 and 2007, but none in the tunnel itself. There is presently no available information on tunnel fires occurring in combined- use tunnels. CHAPTER FIVE COMBINED-USE ROAD TUNNELSâLITERATURE REVIEW
28 FIGURE 5 Tunnel with pedestrian walkways all along the tunnel for pedestrian crossings (San Francisco). FIGURE 6 Tunnels that accommodate bus stops (Seattle). FIGURE 7 Whittier Tunnel interior: combined-use for road and railway vehicles. FIGURE 8 Cross section of the Drogden Tunnel (dimensions in millimeters).