If a piece of pine wood is left in the backyard, it will basically be explained in this life: it will turn black, grow mushrooms, crack cleanly, and one day be carried away by termites. But if chosen as a railway sleeper, this wood is like going to another world for training - fearless of crushing, it can still maintain its bone shape when retired. Don't worry, I know what you're thinking: Isn't this just soaking wood in oil? It's so amazing, it's not zero pollution, and it's no longer needed on high-speed rail lines. All of what you said is correct, but its strength lies precisely outside of these "shortcomings", with a kind of toughness like that of an old cannon in the martial arts world.
Why is the difference between humans and chimpanzees even greater when they both come from pine wood backgrounds? The answer is in two words: soaking oil.
Choosing pine wood for sleepers is because it is straight enough, not lacking, and easy to penetrate. The woody tracheids of pine wood open their doors and are suitable for oil immersion renovation. The core logic of the so-called oil immersion process is to infuse "insect repellent and decay repellent" into the soul of wood. After drying the pine wood, it is loaded into an oil immersion tank. First, the internal air is evacuated, and then hot anti-corrosion oil is poured in. Then, high pressure is applied to allow the oil to penetrate deeply. This force forced the oil to continuously drill inward, with depth increasing layer by layer, ultimately settling on a minimum number of 13 millimeters or more. The wood is no longer pure wood, but has grown a dense and unappetizing layer of "oily skin". Fungi 'enzymes cannot gnaw on this layer, termites' antennae bounce off when they touch it, and rainwater only slides off without even giving them a chance to stay.
Of course, this layer of "oily skin" also puts an environmentally friendly burden on the sleepers. It is inevitable that there will be oil dripping from the railway after a long time, which is not a glorious thing. In the era of rapid railway development, this oil soaked wood is almost the only cheap choice that can withstand heavy outdoor loads. It is said to be powerful not because it is perfect, but because it can make a piece of pine wood that has been rotting for three years carry a train roaring for decades without falling apart. Even if the surface of the sleepers cracks, the more than 13mm soaked layer still holds the bottom line for it. In terms of buffering, it is softer than concrete sleepers and can crush the force of the wheels rushing down before handing it over to the ballast; In terms of "self-healing", the elasticity of wood fiber will make you hear a low-key sound when you walk beside the old railway, rather than the hard and crisp concrete.
There is no such gentle place along the railway. Steel rails can cook eggs in summer, and freeze colder than ice in winter. Sleepers not only have to withstand thermal expansion and contraction, but also have to cushion sudden heavy pressure. Coincidentally, precisely because the wooden billet itself has elasticity, its flexibility remains even after being soaked in oil. When a train passes over it, it can deform slightly, dissipating some of the impact and healing the ballast and roadbed.
Really, some wood is so powerful that it takes decades and countless tons of weight to understand.
