People who are engaged in railway maintenance are somewhat ill at work - they want to touch wood and kick stones. I have no idea. I have to deal with sleepers and ballasts every day. After a long time, I have an inexplicable feeling for these things.
Sleepers first. You can see it at a glance on the railway, it's black and shiny, like paint. In fact, it's not painted, it's the color immersed in the oil. The raw material is pine, which grows fast and is cheap in the mountains. Pine wood furniture is generally soft and easy to knock out pits, but it is suitable for making sleepers - enough, the key can also be supplied in batches.
However, the pine has a problem and cannot be released. You fell a pine tree and threw it into the field. In a few years, the insects first nibbled, then the mould followed, finally rotted into a beach. If the railway sleepers are of such virtue, what kind of railway should be built, directly change to mushroom.
Therefore, the pine must be "rescued" by oil immersion.
The process is not too sketchy. Professional anti-corrosive tank: plug the wood in, first clean the air inside, open the pores, and then fill the anti-corrosive oil and pressurize it. The oil is drilled along the fiber of the wood to a very deep depth, generally 13 mm. Cut off the treated sleepers to see whether they are black on the outside and black on the inside. The color changes from outside to inside.
With such a struggle, pine trees that had to be replaced for several years could be carried for decades in the wild. It can be carried by the wind, sun, rain and snow.
Sleepers alone are not enough.
You see, there is a layer of crushed stone under the sleepers, called ballast. Some people think it is random filling stone to press, in fact not. The shapes of those stones are required, they must be angular and cannot be round - round stones roll against each other and cannot be pressed; Only those with edges and corners can be engaged together to form a whole.
The role of gravel is explained by three things: supporting the sleeper, dispersing the pressure and draining the rainwater. The hundreds of tons of things from the train pressed over, the strength was not small, and if there was soft soil under the sleeper, it deformed in a few days. The gravel layer is hard and air permeable. It can be dispersed by force and drained by water seepage. In this way, sleepers do not need to be immersed in water. Their service life will be longer with their own anti-corrosion capacity.
The railway is like this. It looks simple and there are all gateways under it. A black wood, a pile of broken stones, not eye-catching, no train could run without it.
