Why put a lot of pebbles on the railway?

When we take the train, we often see a lot of rubble under the tracks. Many people think that when a train is built on a dirt road, there will naturally be a lot of rubble. In fact, these small stones were put up artificially. The technical term for these small stones is ballast. Ballast is gravel used to support track sleepers in railway transportation system, and it is a common ballast structure. Railway engineers will lay a layer of gravel on the subgrade before laying the rails, then tamp it, and then lay the sleepers and rails.

The function of ballast is to increase the stability of the rail. Using ballast can facilitate drainage and adjust the track position. At the same time, because the ballast disperses the weight of the train and track on the subgrade, it can reduce the vibration and noise generated when the train passes and increase the comfort of passengers.

Disperse the power of vibration and enhance the drainage function. Ballast can also disperse the vibration and high heat generated when the train passes, keep the track gauge of the rail unchanged, avoid derailment accidents, reduce noise, and quickly discharge rainwater from gaps between stones. If stones are not paved, when it rains, the drainage function will be blocked, which will loosen the soil under the rail and the rail will fall; In winter, frost columns will be generated under the rails, and the rails will float upwards.

However, the ballasted track is not as strong as concrete, and the gravel will shift due to the train pressure, so it is necessary to regularly correct the track position and supplement the gravel; Ballast has a large drainage capacity, which will also make the rails overgrown with weeds and have high maintenance cost.

High-speed railways in many countries in the world are ballastless tracks. However, the high-speed railways in France are all paved with gravel. The key point is that when the train runs at high speed, it will have a strong airflow influence on the surrounding area, and so will the cornerstone (ballast) under the train.

An old master who has worked on the railway for 20 years told me that although the pebbles on the railway are inconspicuous, there are many articles inside. Without these pebbles, the safety of the train could not be guaranteed at all.

When I was at school, my home was separated from the railway by a wall, and the railway on the other side of the wall could be seen from upstairs.

When I am bored, I always like to lie prone on the window, look at the railway on the other side of the fence and count how many trains have passed. Each train has several carriages.

With the increase of times, I suddenly realized a question, why are there so many pebbles on the tracks? At that time, because I was still young, I thought that these rubble were all rubbish that was not cleaned up when repairing the railway.

Until I joined the work, I met an old master who had worked on the railway for more than 20 years by chance. Under his answer, I realized that the pebbles laid on the railway are called ballast, and the main functions of ballast are as follows.

Distribute the weight of the train more evenly on the subgrade. Ordinary train cars weigh about 70 tons, and long-distance trains usually have 16 cars. The total weight of a train is 1000 tons, which is still in the case of no load. If it is carrying passengers or full of goods, the weight of the train will increase exponentially.

When the train runs on the rail, the weight of the train itself is transferred to the subgrade through the rail, sleeper and ballast, and the sleeper bears considerable pressure. Although there are very strict compression requirements for sleepers and subgrade when building railways, a large number of trains pass on the rails every day. After a long time, sleepers and subgrade will sink.

Therefore, it is necessary to spread ballast evenly on the rails to disperse the pressure of sleepers. By increasing the effective area and reducing the pressure per unit area, the pressure on the subgrade will be more uniform.

Prevent the track from moving. Aren't all the tracks fixed? Will there really be displacement? The answer is yes, but this displacement is so slight that it is difficult for the naked eye to detect it.

When the train passes through the curve, the rail needs to provide the centripetal force needed for the train to turn, and its reaction force will urge the rail to move in the direction of the outer rail; When going uphill, the reaction force of locomotive traction will also cause the track to shift.

Of course, this displacement is not permanent, and the track will soon return to its original position after the train passes.

Laying a railway with ballast, so that the ballast tightly wraps the sleepers, can reduce the movement of the rails and limit the rails to a safe range. If there is no ballast, once the track has a large displacement, the probability of train derailment will increase indefinitely.

Absorb the impact when the train is running, that is, absorb the impact. When the train is running, the steel wheels roll on the rails. When the running speed and the weight of the train add up, the wheels will have a considerable impact on the track, and the instantaneous pressure on the track is twice the static weight of the train.

Unlike cars, trains have no rubber to absorb the impact. If such a powerful instantaneous impact force is not solved well, the following three problems will appear:

First, it will lead to subgrade subsidence.

The second is to make passengers feel bumpy and affect the ride experience.

Third, the impact force reacts on the rail, which will lead to the fracture of fasteners, sleepers and rails.

It is precisely because of these problems that a relatively soft ballast is needed as a buffer between steel collisions to absorb this powerful impact and provide shock absorption for trains. Of course, the "softness" of ballast is only relative to wheels and rails. It's not soft at all.

Ballast also has the function of drainage. Drainage on the railway track can not be achieved only by drainage ditch. Ballast is very important for drainage.

When it rains, ballast can quickly make rainwater penetrate into the ground and improve the overall drainage capacity of ballast bed. If there is no ballast on the rail, the rainwater cannot be discharged smoothly, and the subgrade and sleeper will be soaked in rain for a long time, and their strength will also be affected.

Once the roadbed is eroded, or the sleepers become fragile, it is very easy to have accidents when the train passes by.

Therefore, drainage is a function that must be reversed.

Can all kinds of stones be used as ballast? Of course not. In the eyes of most people, ballast is just a pile of stones under sleepers, but not all stones can be used as ballast.

Ballast should have enough strength to bear the pressure transmitted by sleepers. If the strength is not enough, the pressure brought by the train will crush the ballast. When the train passes by, the vibration will cause the ballast to collide and rub against each other. If the ballast strength is not enough, it won't be long before the ballast is worn out.

At the same time, the ballast should have strong corrosion resistance. The "corrosion" here is not man-made, but in the face of changes in the natural environment. It is not easy to expand and crack in high temperature environment, not easy to freeze and crack in cold winter, and not easy to be eroded by rain.

In addition to the above two points, the most important point is that the stones selected for ballast must not be "smooth". It must be angular, and the more irregular the shape, the rougher the surface. Only in this way can the ballast be firmly held together. If the stone is too smooth, the ballast will be scattered all over the floor.

Ballast is a pile of stones, but it needs regular maintenance. In our mind, the railway track is bound to break, shift and wear when it is crushed and rubbed by the train for a long time, and the staff should maintain the railway track regularly.

What many people can't think of is that the ballast piled up by pebbles also needs regular maintenance.

As the train runs, the ballast will become very dirty. The gap between ballast is filled with worn ballast fragments, sleeper fragments, spilled cargo fragments and dust. After gap filling, the drainage performance of ballast becomes worse, which affects the strength of this subgrade.

At this point, it is necessary to "filter" the pebbles.

The process is also very simple. First, dig out the ballast, clean up the debris on it, backfill this pile of pebbles, and finally vibrate and compact the backfilled ballast. In this process, it is necessary to pick out the severely worn and smaller stones and fill new stones into the ballast.

It is said that in the end, on the railway, seemingly insignificant pebbles can play such a big role. Without these pebbles, the safety of the train could not be guaranteed at all.

As for why the high-speed rail does not use ballast, it is mainly for safety reasons. The speed of high-speed trains is much faster than that of ordinary trains, generally more than 300 kilometers. At such a fast speed, it is easy to take pebbles off the track and fall off the viaduct. Once it hits passing vehicles and pedestrians, it is as powerful as a bullet.

I believe everyone has such a question, why is there a lot of gravel under the train track? The high-speed rail, which is also a railroad track, rarely sees such a scene. What's the difference between them?

Why should gravel be laid under the train track?

Because the quality of the train is particularly large, it will also produce great pressure when passing by, so the gravel will play a role!

This kind of gravel pavement is called ballast, and the stone is usually super-grade granite.

Ballast is coarse gravel or crushed stone used for laying on railway subgrade. Its main purpose is to disperse the pressure of trains and tracks, lay some gravel, and reduce the huge noise and vibration when trains pass by.

ballast

As an important part of railway track system, ballast supports track sleepers, rails and trains.

When building a railway, the road surface should be opened first, then a layer of gravel should be laid on the subgrade, and then sleepers and rails should be laid.

Another advantage of using these gravels on the railway track is that they can play a good drainage role, because there are many gaps between the gravels and they are also higher than the road surface. When it rains, the rain will leak down, so that the rails will not get wet, the sleepers will not be corroded by the rain quickly, and the freezing damage can be prevented.

In addition, it is convenient to adjust the position of the track. Gravel can also disperse the weight of tracks and trains on subgrade. When the train passes by, it can reduce noise and vibration. In this way, passengers will feel comfortable, otherwise it will be noisy and bumpy, and the experience for passengers will be poor.

In addition to these benefits mentioned above, it can also play a good role in heat dissipation.

Because the train will generate a lot of heat when driving at high speed, but there is a layer of gravel under it, which can not only reduce vibration, but also disperse heat. Only by dissipating the heat can the distance of the rails remain unchanged, otherwise the track gauge will change, which will easily lead to traffic accidents.

However, the gauge will not change with the heat dissipation of gravel, thus ensuring the safe operation of the train and avoiding derailment accidents.

In addition, weeds can be prevented from growing on the rails, otherwise weeds will be overgrown, which is not conducive to train operation. However, because of the rolling of the train, the gravel will also be pressed to both sides of the road, so in order to maintain stability, gravel will be replenished from time to time.

Characteristics of crushed stone

These rubbings are not smooth and have sharp edges and corners because they are not easy to slide down. Only these irregular broken stones can support the track in a staggered way.

In a word, gravel has many benefits. On the one hand, it can play a good drainage system, bring buffer, protect subgrade and resist lateral and longitudinal resistance from railway tracks.

In addition, the gravel is elastic and has the function of shock absorption and buffering, and the gravel on the train track can also prevent the sleepers from sinking.

Nowadays, the high-speed rail is basically made of concrete monolithic track bed, so most of the high-speed rail tracks are not paved with gravel! The track of the train is divided into ballasted track and unballasted track, and the ballasted track is paved with gravel.

The high-speed rail is very fast and the cars are closely connected. If the track is paved with gravel, the train will fly up when it is running at a high speed, which poses a safety hazard, but it does not rule out that some high-speed rail tracks are also ballasted tracks.

The track of the high-speed rail adopts special vanadium steel, which can reduce thermal expansion and cold contraction, and the track of the high-speed rail is particularly firm, so the staff will maintain it in time when it expands and contracts.

In a word, I didn't know that the gravel on the railway had so many functions. I only know that paving so much gravel has played a very good role in compression resistance, but I didn't expect it to have multiple functions such as shock absorption, noise reduction and waterproof. This is a bit unexpected!

The technical term for these stones is ballast.

The function of ballast is mainly manifested in the following aspects.

One is to transfer the weight of the train to the subgrade. When the train runs on the rail, its weight is transferred to the sleeper through the rail, to the ballast through the sleeper, and then to the subgrade through the ballast. After paving the ballast, the bearing surface of the sleeper will increase and the sleeper will not be pressed into the soil by the train.

The second is to play the role of drainage. Rainwater can be discharged to the drainage ditch beside the railway through the gap between the ballasts to ensure that the foundation under the ballasts is not soaked by rain.

Third, it can reduce the longitudinal impact of the train and make the train run more smoothly. When the train is running, the ballast gap has a good vibration reduction effect.

Fourth, noise can be reduced. Just like we hammer the stone surface and the soil surface, if we use too much force, the echo will be loud.

Fifth, it has the functions of heat absorption and ventilation. When it is hot in summer, the rails are easy to expand, and the ballast can absorb some heat.

Sixth, it is convenient for railway departments to repair lines and replace sleepers. When the sleeper fails, the railway workers only need to pry open the ballast to replace the sleeper; When there is a triangular pit or uneven height on the line (at this time, the train will shake when driving on it), railway workers can eliminate the line disease as long as they knock on the line and let the ballast fall into the pit.

Ballast is generally used for ordinary speed railways. Most high-speed railway lines use integral ballast, but some high subgrade sections also use ballast.

Railways have strict quality standards for ballast used. Quartzite, granite, gneiss and other materials are mostly used for ballast.

In the past, a ballast factory was built inside the railway system. Nowadays, taking the road of marketization, in addition to the internal ballast factory, we also purchase ballasts produced by local enterprises in a market-oriented way.

Why put more stones beside the tracks? I often see them when I take the train, but the ultimate goal is to drive the train safely.

Train tracks are made of steel. In order to reduce in-situ stress, a layer of gravel is often laid when building tracks. The function is to bear the subgrade, disperse the weight borne by the rail, prevent the deformation of the rail, play a buffering role and keep the original position of the rail.

From the economic point of view, gravel has low price, high hardness and high compressive strength. Friction between gravel can absorb some noise and energy brought by trains, and minimize the harm of noise in life to the nearest residents. Using gravel as a stone bed is convenient for the renovation and maintenance of railway tracks in the future and prevents railway water accumulation. At the same time, the stone bed paved with gravel can effectively prevent the growth of weeds and angiosperms, which greatly improves the safety of the train.

Thank you for inviting Wukong! You may wonder why there are many small stones on the train tracks. Don't underestimate the role of these small stones, they are very useful!

First of all, the stone next to the sleeper is called ballast. Ballast is used for railway subgrade. Ballast is a common ballast structure, which is used to support track sleepers in railway transportation system. Before laying the track, the project will lay a layer of gravel on the subgrade, then compact it, and then lay the sleepers and tracks. Using ballast can facilitate drainage and adjust the track position. At the same time, because the ballast disperses the weight of the train and track on the subgrade, it can reduce the vibration and noise generated when the train passes and increase the comfort of passengers.

Its main functions are:

First, it can reduce the vibration and bump of the carriage;

Second, in rainy days, gravel subgrade is beneficial to drainage;

Third, gravel subgrade is not easy to freeze!

In addition, it can prevent gauge deviation and reduce the occurrence of train derailment accidents!

An old master who has worked in the railway works section for 12 years said: When you see pebbles on the railway, you'd better not pick them up. Once the stones beside the tracks are removed, the moving train may derail and roll over. Small stones may seem unremarkable, but their functions cannot be ignored.

Trains are the means of transportation that people often contact in their lives. Convenient and fast, it has more advantages than airplanes and ships. Whether it is safety or ticket price, it is more acceptable to ordinary people. When you take the train, you can often see a layer of stone on the track, which is not beautiful. So the question is, what are the functions of these stones?

Stones on the railway should not be used indiscriminately. Some people noticed that there were stones around the tracks. Ordinary people don't know its function and think it is just a common stone in life, and there is nothing special about it. But the insiders are different. They call this ballast. If you just say this word, many people still don't know what it means.

Ballast is a small gravel of granite, which is laid on the railway track after treatment. Although the small stone is inconspicuous, it can ensure the smooth operation of the train. The staff of the railway system engineering team will regularly inspect and maintain the railway ballast to avoid being damaged.

Ensuring the good condition of railway lines is the basic guarantee for the safety of train operation. When laying the line, the railway department will strictly control the materials. Take small stones for example, they can be found everywhere, and some are still very cheap, but the stones laid on the train are exquisite, and not all stones can be used.

First of all, the stone is preferably granite. Magma cools underground for a long time, forming a hard crystal structure, which is more stable than other materials. Its own structure will not change due to the high temperature of the railway track, thus affecting its bearing capacity.

If ordinary stones are used casually, even if the tracks are covered with a thick layer, hundreds of tons of trains will fly by. Under the great impact, the structure of the stone will change, crack or crush, and it will not play a stabilizing role. After the tracks move, the next train will have great safety hazards.

Small granite rubble is used as ballast, which makes the structure more compact and increases the compressive strength. When the train passes through the track, it can bear huge impact force, disperse part of gravity and ensure that the track is not affected.

Secondly, the stones laid on the railway look irregular in shape and sharp in edge, and even scratch your fingers when you hold them in your hand.

Maybe someone will ask, wouldn't it be better to smooth the edges of these stones before paving them? This is a wrong idea. The smoother the stones are stacked, the easier it is for them to slide off each other. On the contrary, they can't provide enough support for the rails and lose the meaning of protection.

In nature, the surface of round pebbles is smooth. If they are laid on the rails, the ballast will disperse immediately. When the train passes through the tracks, it is not strong enough underground, and there may be flying sand and stones scattered in all directions, damaging the parts at the bottom of the train.

If you use sharp-edged stones, criss-crossing together, there are more support points, which can ensure greater stability in the face of strong pressure. There are gaps between stones, and rainwater can penetrate into the ground smoothly, so as to prevent the roadbed and ballast from being too wet and corroded.

The role of pebbles on the railway If there are no pebbles on the railway, the rails will be directly laid on the subgrade, and the train will pass quickly from above, and the rails may not be able to bear the weight and sink, so pebbles play a vital role.

I have consulted a master who has worked in the railway works section for 12 years, and finally know the role of stones in the railway.

First, disperse pressure and reduce noise.

A train, with its own weight reaching several hundred tons, will have a great impact on sleepers and rails when passing through the line. If there is no object to share the pressure, the consequences will be unimaginable.

The early trains were not so fast and the power was not strong enough. The rails are all made of wood, which can withstand the pressure of the train. /kloc-in the 0/9th century, railway tracks were laid on train lines. Although the speed is very fast, the stress increases, so the technicians have formulated countermeasures to lay a layer of gravel around the track to form a ballast bed.

When the train passes the rail, the steel wheels rub against the rail surface, which will produce great vibration and sharp and harsh sound, which can be felt by the passengers inside.

Laying pebbles under the sleepers of the railway track can disperse the heavy pressure of the train on the ground, reduce the pressure of the railway track and avoid the risk of displacement. In addition, the crystal structure of the stone can also absorb some noise, protect the roadbed and make the passengers in the carriage feel less noisy.

Second, speed up heat dissipation and prevent rail deformation.

Under the influence of high temperature, the structure of metal changes, and the surface will sag or crack, especially in a sealed environment, the heat generated cannot be dissipated in time, and the influence degree will be aggravated.

Imagine that the moment the train touches the rails, the high temperature generated is as high as Baidu. If it is a cement subgrade, the heat dissipation will be blocked, and the train tracks will be deformed after running several times.

Small stones with irregular shapes, piled together, can produce greater bearing capacity, and there are gaps between the stones, which is beneficial to air circulation, radiate the heat of the rail evenly to the ground, and quickly cool down to prevent the rail from being deformed due to high temperature.

Third, it is conducive to adjusting the route.

The railway tracks have been in the wild for many years, and the wind and the sun are shining. In this environment for a long time, the problem of aging is inevitable and its position will shift. It is necessary for railway maintenance workers to make corrections, lift the railway track with a rail crane, lay stones under it, adjust the ballast height, and restore the railway track to its normal position.

The stones under the sleepers can be more or less, which is convenient for adjustment. Maintenance personnel can adjust the track line of the railway in this way.

Fourth, keep the track gauge to prevent derailment.

According to the characteristics of metal, due to the influence of temperature difference, the rail will obviously expand with heat and contract with cold. In fact, you can see with the naked eye that after the train passes through the tracks, there will be a slight bending change, which will not last long and will soon recover. The stone under the sleeper worked.

Sleepers and rails are cross-structured, supported by pebbles around them, and the lower part of the rails is tightly wrapped, so that even under strong impact, a proper gauge can be maintained to prevent the rails from moving and to control them within a safe range.

Write it at the end

The tracks will inevitably shift under the heavy weight of the train. The small stones below protect the railings. However, the environment of the railway line is harsh, and stones may be scattered at various positions, which requires regular maintenance by staff to ensure the safety of the train.

The main function of these small stones is to absorb shock.

Because if there are not enough pebbles under the rail, the train will be unstable after passing the rail, and it will also cause severe vibration;

In addition, the weight of more than a dozen cars, plus the goods and passengers carried, is enough to cause the rails to sag downward. If you don't put pebbles, the train won't run;

Also, if pebbles are not paved, it may block the drainage function of the road when it rains, resulting in loose soil and collapse of the railway track.

Finally, no matter where the track sinks, small stones can be filled in immediately!

This kind of gravel you mentioned is called ballast, mainly the gravel of railway subgrade, which is mainly used by railway to support track sleepers. This is the most common ballast bed structure. First, lay a layer of gravel on the subgrade, then compact it with special equipment, and then lay sleepers and tracks, which can reduce the vibration and noise caused by the train passing by and make passengers more comfortable!

In our life, we will find many broken stones laid beside the railway tracks. What is the function of the broken stone head?

Reduce the pressure of the train on the ground and stabilize the subgrade.

Rails are laid on flat land. Because the contact area between the rail and the train wheel is very small and the weight of the train is very large, according to the physical formula (contact area of pressure and weight), the pressure on the rail is very large. Laying sleepers and crushed stones under the rails can effectively disperse the weight of the train and prevent the rails from sinking into the soil due to excessive pressure, which will cause instability of the railway subgrade and affect the driving safety.

In addition, the pavement paved with soil is easy to deform, and gravel heads can be placed under the sleepers to level the pavement. When it rains, the rainwater can be discharged in time through the gaps between the gravel to avoid the wooden subgrade from being softened by water. In winter, gravel subgrade will not raise the railway track because of the freezing and expansion of water. Gravel can also reduce the growth of weeds without affecting driving safety.

Absorb the high heat generated when the train passes through the rails.

Trains passing through the rails at high speed will produce high heat, and broken and irregular gravel will be spread between the rails. Because this kind of gravel is easy to break, it can consume part of high heat after absorbing it, thus reducing the influence of high heat on subgrade and rail and ensuring the safe operation of the line.

If you don't pave the gravel head, or pave the round stone, because the round stone is not fragile, it won't absorb high heat.