Why Potholes Form on Roads

Roads that were fine suddenly develop holes the size of a pot overnight. In Korea alone, over 500,000 are created and filled each year. Why do roads that can withstand trucks weighing tens of tons suddenly break apart after it rains? The culprit is water. When water seeps into the asphalt cracks and freezes on a winter night, it pushes the road apart from the inside. That's why nowadays, instead of blocking water, they use permeable pavement that allows it to pass through and drain. Apparently, less water splashes up on rainy days for the same reason...