Friends who live next to the railway line should know that there is a dense layer of stones under and even on both sides of the railway line, and this layer of stones also has a name that is unique to itself, that is , ballast . Do you know what this thing is for? Why do some people want to pick up some "pebble" to go home, but they are strictly stopped or even warned by the railway staff?

The so-called ballast is actually the gravel used to lay the railway or highway subgrade . Especially for railways, when fast and heavy trains whizz past the railways, if there is no "ballast" to disperse the impact force, then the sleepers and even the railways will be deformed soon. It needs to be replaced in a very short time, which not only consumes a lot of manpower and material resources, but also greatly affects the efficiency of railway traffic.

It is precisely because of this that the ballast, which can disperse the weight of trains and rails on the roadbed and play the role of "pressure relief", can be said to be an indispensable link in the early stages of railway construction in various countries. In addition to "pressure relief", Ballast also has other "five abilities".

First, reduce noise.

When objects collide violently, a lot of noise is often generated, and the friction between the train and the rails is quite harsh. Therefore, how to reduce the noise was once a problem that many researchers wanted to solve. In the end, they found that the answer was very simple. As long as the ballast was laid under the sleepers, the sound caused by the friction between the train and the rails could be effectively reduced.

Second, speed up the heat dissipation.

The severe friction of metal will form a lot of heat in a short time, especially when the surrounding is full of cement or land, the heat dissipation will be further slowed down, and if this heat cannot be dissipated as soon as possible, it will cause damage to the rails. Certain damage, in severe cases, even endanger the lives of passengers. And all of this is not a problem in the face of "ballast", the gap between the pebbles can greatly speed up the heat dissipation of the rails.

Third, reduce vibration.

Improving comfort as much as possible is a major pursuit of people's transportation, especially for long-distance transportation such as trains, the poor riding experience is undoubtedly a torture. The original train vibrated very violently when it was running. It was not until the "ballast" was applied that the bumpiness of the train was greatly reduced. If there was no layer of seemingly ordinary stones, many passengers might You will vomit upside down on the train.

Fourth, prevent water storage.

A large section of the railway is directly set in the open space, which means that it has to directly endure the invasion of wind and rain. Without ballast, it is easy to store water on the railway, which will accelerate the corrosion of sleepers. , posing a huge threat to the safety of trains. With the layer of small stones under the railway, it is very different. The water flow will disperse along the gaps between the stones, which greatly reduces the difficulty and frequency of railway maintenance and prolongs the service life of the railway.

Fifth, prevent grass growing.

Whether from the perspective of aesthetics or safety, no plants should be grown on the railway, which means that it is not feasible to lay sleepers directly on the ground, and the only options are pouring cement or laying ballast. And pouring cement can not fundamentally solve the problem. After the violent vibration causes the cement to break, the plants will still grow out. Therefore, it is better to lay the ballast directly once and for all.

It is precisely because of its rich functions that not all small stones can act as "ballast". Those stones must have the characteristics of tough texture and not easy to weather. Like Chinese ballast, the material is basically super granite . It can be used for a long time after laying.

Then some friends may ask, is ballast laid on all railways? The answer is of course no. For example, China's ballast bed is divided into two categories, namely ballast ballast bed and integral ballast bed . As for why there is an integral ballast bed without ballast, it is mainly due to the following two reasons.

First, ballast is mainly used in the open air.

For example, some non-open-air environments, such as tunnels or bridges, are not suitable for laying ballast at all, not to mention how difficult it is to lay it, and how high the cost of later maintenance is. It is only the unique geographical conditions. Can make the ballast ineffective. At this time, choosing to lay ballast is not worth the loss, and it is better to directly choose to pour concrete.

Second, the use of ballast to lay under the railway also has drawbacks.

When the train is running at high speed, it is easy to cause a strong impact air flow, which will wash away the ballast, and even make it splash around and hit other vehicles. Therefore, basically, high-speed railways in various countries use concrete units. Ballast acts as a cornerstone. Otherwise, when the speed of the train can easily reach five or six hundred kilometers per hour, the surrounding area of ​​the railway will become very dangerous. Generally speaking, the ballast will be laid under the railway only if the speed of the train is relatively slow.

In addition, the regular filling of ballast is also a problem. Even if the train speed is relatively slow, the ballast arrangement will be deformed after rolling day after day. Therefore, there is the trouble of ballast bed, and many countries choose to pour concrete directly. One of the reasons for laying a monolithic track bed.

In this case, does it mean that the integral track bed will gradually replace the ballast track bed?

Not really. With the advancement of science and technology, people have gradually developed products that can bond ballast. In this way, the goal of removing the cumbersomeness of ballast can be achieved on the basis of retaining its many advantages. Ballast bed still has a wide range of application space and good realistic prospects.

Ballast is so important that it's not hard to see why railroad workers don't let people pick it up. What do you think about it?