Pore water pressure

Pore water pressure is the pressure of the water that is inside the tiny little spaces (called pores) inside things like dirt, rocks, and sand. Imagine that a sponge has tiny holes that water can get inside and sit in. If you put too much water into the sponge, the water itself has a pressure that it can push on the sponge walls. This same pressure happens inside dirt, rocks, and sand, but is much much harder to notice.