Stones are laid in switchyards to increase the resistance of soil which leads to reducing the limit of touch and step potential.
They also prevent the formation of puddles and accumulation of water in the switchyard which is not a good sign in the case of high-voltage equipment.
Stones also protect against the entry of wildlife animals and snakes, lizards, rats etc.
in the substation area. They eliminate the growth of small weeds and plants inside the switchyard or transformer yard.
They protect the moisture content evaporation and keep the ground wet. Finally, they prevent insulating oil spillages from catching fire easily.