To be honest, when people hear "wooden sleepers", their first reaction is: Is it reliable? The era of steel cement, still using wood?
Hey, don't you say it, it's used, and it's used a lot on the bridge.
It starts with running trains on the bridge. You might think, bridge, maybe heavy. A train with hundreds of tons or thousands of tons is forced over, so it shall not collapse? That's true, but the reason why engineers really cannot sleep at night is not the weight of that moment - but the "chatter" of years and years.
What is fibrillation? When the train wheel rolls over the rail, the rail transfers the force to the sleeper, and then the sleeper unloads the force to the deck structure. This process comes once every group of wheels. One train has thousands of wheels, dozens of times a day and thousands of times a year. This repeated, subtle, and never - ending vibration, known as "fatigue load," translates into plain language - you are not knocked down by a hammer, you are knocked a little every day, knocked a little, knocked a day suddenly found: broken.
Therefore, the track materials on the bridge shall not only bear the weight, but also bear the "gentle suffering".
At this time, the wooden sleepers appeared.
Pine wood, as the main wood of sleeper, is not randomly selected. Pine fiber structure has natural elasticity and will slightly rebound after being stressed, not as hard as some materials. To make an analogy: reinforced concrete is the "iron merit". If you collide with me and I collide with you, both will be damaged; Pine is the "Taichi Pusher". I give way when you come. Remove most of the energy and send it back. This flexibility makes wooden sleepers more temperamental than pure hard materials in a bridge where "overcoming rigidity with softness" is needed.
But wood has a natural weakness - fear of water, insects and decay. If you put a bare pine sleeper on the bridge, exposed to the wind, sun and rain, it will be rotted into slag in a few years. This leads to the "full equipment" of wooden sleepers: oil-immersed anti-corrosion process.
In short, the processed pine sleepers are sent into a sealed large tank, and the vacuum is firstly pumped to "scare" the air and water in the wood cells, and then the preservative oil is "stuffed" under high pressure. The high pressure forces the oil to seep into the wood, deep and thorough. Through this operation, the immersion depth can reach more than 13mm - don't forget this figure, which means that the wood surface has been firmly "locked" by the anti-corrosive oil when moving more than one centimeter inside. No water, no insects, no fungus to find the mouth.
The most beautiful part of this process is that it does not wear a "rain coat" on the wood, but makes the wood itself a "iron wood man". The preservative oil penetrates into the wood fiber and is integrated with the wood. It is not applied on the outside to wait for the peeling off of the paint. Even if you grind off a layer on the surface of the sleeper, the inside is still in anti-corrosion state.
Therefore, the oil-immersed pine sleeper is used on the bridge, which is a pair of "Tianchou CP". The pine itself has elasticity, which can absorb vibration and protect the bridge steel structure from repeated vibration damage; Oil-immersed treatment allows it to withstand the humid, wind-blown and sunlight environment on the bridge. It is lighter than the steel sleeper and easy to lay and maintain; Feet feel softer than concrete and more friendly to bridge structure.
Of course, if you think "wood is not as rigid as steel", it's OK. But engineering never depends on who is harder, but who is more suitable. Running a train on a bridge requires not an iron "hard man" sleeper, but an "old man" who can carry bullets, resist construction and share worries for the bridge at a critical moment.
Oil-immersed pine sleepers, do this work: do not fight for fashion, silent.
