Why should gravel and wood be laid under the traditional railway?

The rail stands on the soil, because the contact area between the rail and the train wheel is small, but the train is heavy, so the pressure on the rail is quite large (pressure = weight ÷ contact area). Therefore, sleepers and stones must be laid under the rails to disperse the weight of the train and prevent the rails from falling into the soil because of too much pressure.

Why put stones under the tracks? It is because the rails and sleepers must bear the weight of the train for a long time, and one of the tasks of the gravel head is to prevent the rails from sinking. In addition, the train passing through the rails at high speed will produce noise and high heat, and the other two important tasks of the gravel head are noise absorption and heat absorption. If you pay attention, you will find that the stones laid between the rails are all chipped and very irregular in shape. Such a stone is easy to break, and the high heat generated when the train passes can be absorbed because of the breaking of the stone; If the pavement is round and smooth stone, because it is not easy to break, the heat absorption effect is not good!