At a casual glance, they might look like regular pebbles, but if you ride on trains frequently, you may have noticed that regardless of the country in which you're traveling,

乍看之下，它們可能看起來像普通的鵝卵石，但如果你經常乘坐火車旅行，你可能會注意到，無論你身處哪個國家，

the shape and texture of those stones are almost always the same—all across the globe!

這些石子的形狀和質地幾乎都是相同的——無論在世界上哪個地方！

So what's the reason behind that? 

所以其背後原因為何呢？

Why do such otherwise unremarkable rocks line our planet's railway tracks? 

為什麼這些看似普通的石子會排列在鐵軌上呢？

The crushed stones that line railroad tracks are collectively called track ballast.

鐵軌上排列的碎石統稱為道碴。

More specifically, the track ballast constitutes the trackbed upon which sleepers or railroad ties are laid.

更具體地說，道碴構成枕軌，鐵軌枕木就鋪設在其上。

As you may have seen, these stones are packed below, between and around the railroad ties.

你可能看過，這些石頭堆在枕木的下方、中間及周圍。

The thickness of the track ballast usually ranges between 25-30 cm, and varies depending on certain conditions pertaining to the geographical location of the railway track. 

道碴的厚度通常在 25-30 公分之間，根據鐵軌位置的特定條件有所不同。

Track ballast usually consists of crushed rocks or stone, but in some cases, less suitable alternatives, like burnt clay, are also used.

道碴通常由破碎的岩石或石頭組成，但在某些情況下，也會使用不太適合的替代材料，例如燒製黏土。

However, it's important to understand that you can't just throw a bunch of rocks on a railroad and be done with it. 

然而，重點是，並不是把一堆石頭扔在鐵路上就算完成了。

As mentioned, the stones in the track ballast have a characteristic shape, size and texture.

正如前面提到的，道碴有特定形狀、大小和質地。

Their surface is not smooth and their edges are jagged, and for good reason.

它們的表面並不光滑，邊緣也是鋸齒狀的，這是有原因的。

These rocks interlock with each other and therefore stay in place.  

這些岩石的邊緣咬合在一起，因此能夠固定在原處。

If you replace them with circular or smooth rocks, they would slide over each other and compromise the strength of the track ballast.

如果改用圓形或光滑的岩石，它們會滑動，從而損害道碴的強度。

As you might imagine, this can have catastrophic results. 

正如你所能想象的，這可能會帶來災難性的後果。

Railway tracks are made of steel and other metallic parts that are prone to corrosion and rusting, as they are constantly exposed to the forces of nature,

鐵軌由鋼鐵和其他金屬部件製成，容易受到腐蝕和生鏽的影響，因為它們不斷暴露在大自然的作用下，

including extreme heat from the sun, rain, vegetation and general wear and tear.

包括來自太陽的極端高溫、雨水、植被和一般的磨損。

The primary reason behind the existence of track ballast is to protect the railway track.

放置道碴的主要原因是為了保護鐵軌。

It does this in a number of ways. 

它利用多種方式達到這目標。

1. Holds the sleepers in place.

固定軌道枕木的位置。

Many trains, including cargo and passenger trains, roll by on railway tracks every single day. 

每天都有許多列車，包括貨運和客運列車行經鐵軌。

Therefore, it's not surprising that those tracks must constantly withstand a great deal of stress and pressure. 

因此，不難理解這些軌道必須持續承受巨大的壓力和負荷。

Track ballast holds the sleepers in place, so that they don't move longitudinally or laterally when heavy trains roll over them.

道碴固定枕木，使其在重型列車通過時不會縱向或橫向移動。

Without track ballast, those sleepers might give away under the constant pressure of passing trains.

若沒有道碴，枕木可能會在列車不斷通過的持續壓力下變形。

2. Load distribution.

2. 負載分配。

Trains are immensely heavy and exert massive pressure on the tracks and sleepers. 

火車極為沉重，對軌道和枕木施加巨大的壓力。

Since stones in the track ballast are jagged, they interlock with each other.

由於道碴的形狀不平整，它們能夠相互咬合在一起。

This way, the immense load that's exerted on the sleepers and track gets distributed evenly through the track ballast. 

這樣一來，軌道和枕木承受的巨大負荷量能夠均勻地分散到道碴上。

3. Vibration dampening.

3. 減震。

Track ballast absorbs the vibrations caused by a moving train.

道碴吸收列車行駛時產生的震動。

The cushioning effect provided by the stones in the track ballast adds o the comfort of passengers riding in the train. 

道碴提供的緩衝效果增加了乘坐火車的乘客的舒適度。

To test this, next time you ride in a train, pay close attention to how you feel when the train passes over a stretch of railway track without track ballast.

為了測試這一點，下次你坐火車時，請特別留意當火車通過一段沒有道碴的鐵軌時的感受。

4. Drainage.

4. 排水。

It's important to ensure that railway tracks don't get flooded by rains or water clogging. 

確保鐵軌不被雨水淹沒或堵塞非常重要。

Track ballast comes in handy in this regard too. 

在這方面，道碴也很有用。

It prevents water clogging or the accumulation of water on or around the sleepers. 

它可以防止水滯留或水在枕木周圍積聚。

Without it, water would accumulate on the tracks and cause rapid rusting of their metallic parts. 

沒有它，水會在鐵軌上積聚，並迅速讓其金屬部件生鏽。

5. Prevents vegetation around the tracks.

5. 道碴可以防止鐵軌周圍的植被生長。

Although we all enjoy swaths of land filled with green grass, plants and trees, vegetative growth can wreak havoc on the strength of a railway track.

儘管我們都喜歡綠草、植物和樹木覆蓋的廣闊土地，但植被的生長可能對鐵路軌道的強度造成嚴重破壞。

It's extremely important that there is no growth of grass, weeds or plants around the tracks.

鐵軌周圍沒有草、雜草或植物的生長非常重要。

The stones in the track ballast greatly contribute to keeping out vegetation that could compromise the structure and strength of the track. 

道碴大大地防止了可能危及軌道結構和強度的植被的生長。

6. Noise absorption.

6. 吸音。

A moving train is quite loud, especially to people who are OUTSIDE the train.

行駛中的火車聲音相當大，尤其是對於在火車外的人來說。

The crushed stones in the track ballast offer a larger surface area than a flat plane.

碎石填充在道碴中提供了比平坦表面更大的表面積。

This greatly facilitates noise absorption. When trains move on tracks that don't have track ballast, they are noticeably louder.

這大大便利了噪音的吸收。當火車在沒有道碴的軌道上行駛時，噪音明顯較大。

7. Minimizes heat expansion.

7. 降低熱膨脹效應。

During the summer season, railway tracks tend to expand due to the heat.

在夏季，由於高溫，鐵軌容易膨脹。

Track ballast helps keep this heat expansion to a safe minimum, ensuring the efficacy and safety of the track. 

道碴可以幫助將這種熱脹膨脹保持在安全的範圍內，確保軌道的效能和安全性。

As you can see, track ballast not only protects the railway track and its sleepers from the forces of nature and the stress of a moving train, but also adds to the overall comfort of passengers. 

正如你所看到的，道碴不僅保護了鐵軌和枕木免受大自然的力量和火車行駛造成的壓力，還提高了乘客的整體舒適度。

Looking at those stones, you may think that once they're deposited in the tracks, they just lay there forever, without ever being disturbed.

看著那些石頭，你可能會認為它們一旦被放置在軌道上，就會永遠固定在那裡，永不受到干擾。

Well, that's not quite true.

這其實不太正確。

If the ballast is covered in too much dirt or mud, it will affect its effectiveness; it can cause debris to accumulate between the stones and negatively impact its draining ability. 

如果軌道石床被覆蓋了過多的灰塵或泥漿，它的效果就會受到影響，導致碎石之間積聚雜物，並對排水能力產生負面影響。

Just like the railway track, track ballast requires regular maintenance and cleaning. 

就像鐵軌一樣，道碴也需要定期保養和清潔。

Sometimes, the stones are replaced with a new set of crushed stones. 

有時候，這些石頭會被新的碎石替換。

There are also machines called ballast cleaners that specialize in cleaning track ballast, which reduces the amount of manual labor required.

還有一種叫做碎石清潔機的機器，專門用於清理道碴，這樣可以減少人力。

It's amazing how such a seemingly random set of stones constitute the backbone of an industry that affects millions of lives around the world!

看似隨機的石頭竟然構成了一個影響全球數百萬人生活行業的基石，真是令人驚嘆！