Why do holes appear in roads?

Roads that were fine one day suddenly develop holes the size of a pot overnight. In Korea alone, over 500,000 of these holes are created and filled each year. Why do roads that can withstand trucks weighing tens of tons suddenly develop these issues, especially after rain? The culprit is water. Water seeps through cracks in the asphalt and freezes on winter nights, pushing the road apart from the inside. That's why nowadays, instead of blocking water, they use porous pavement that allows water to pass through and drain. Apparently, this is also why less water splashes up on rainy roads.