Various types of civil engineering structures for railroads Civil engineering structures here refer to various structures that are built as the foundation for installing rails. There are various types of structures such as tunnels, bridges, viaducts, and embankments (embankments), not limited to rails on flat ground. The reason is that they must overcome the undulations of the terrain, rivers, wetlands, etc. In fact, in the case of a flat terrain, the rail system is not limited to the flat terrain. In fact, even when the ground is flat, the first step is to build the “roadbed. Since rails, sleepers, and ballast are placed on top of the roadbed, and the train runs on the rails and sleepers, the load on the roadbed is quite heavy. First, a solid foundation must be built to withstand these loads, and this is the roadbed. Of these, it is mainly the earthen roadbed and embankments that are affected by rainfall. Some newer railroads have asphalt pavement or concrete over the roadbed, but not all of them. No matter how much the soil is compacted, it will loosen with heavy rainfall, and in the worst case, there is a risk of collapse. Therefore, from the standpoint of preventing accidents from occurring, restrictions are imposed based on rainfall. The indicators have been reviewed from time to time, referring to examples of disasters experienced in the past. The actual rainfall is monitored using rain gauges installed at key locations along the route. It is important to note that this is not simply a matter of heavy rainfall (i.e., heavy rainfall at the time). Rainfall disasters are often caused by rainwater seeping into the ground, so the question is not only “how much rain is falling now” but also “how much has fallen in total. If the hourly or cumulative rainfall is in balance with the drainage capacity, rainwater can be discharged naturally or through drainage devices (if any) built into the roadbed. However, when rainfall is high, the story is different. The tricky thing is that the drainage capacity varies depending on the topography, geology, and soil conditions of the roadbed, so conditions are not uniform. Concrete viaducts, of course, do not allow water to seep into the structure itself, so the roadbed will not loosen due to heavy rainfall.
The reason why the Tokaido Shinkansen cannot use snow sprinklers to remove snow like the Tohoku, Joetsu, and Hokuriku Shinkansens is related to the above story. The Tokaido Shinkansen, which was built at an earlier date, uses embankments instead of concrete viaducts in many sections, which are more susceptible to the effects of rainfall for the reasons mentioned above. For this reason, the rainfall must be dealt with severely. In other words, sprinkling snow is the same as artificially injecting a large amount of rainfall. This also causes the roadbed to loosen. Therefore, it is not possible to sprinkle so much water that it melts the snow, but only enough to make the snow wet and prevent it from flying up. Sometimes people say, “It’s ballasted track, so it’s ……,” but the main problem is actually the roadbed underneath. On the Tohoku Shinkansen and Joetsu Shinkansen, there are parts of the ballasted track where water sprinkling and snow removal is performed, but underneath the ballast is a concrete viaduct. Therefore, as long as drainage is proper, water spray can be used for snow removal.
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