To excavate is to remove or find by digging. If you have rocky soil in your garden, you may have to excavate it to remove the rocks and replace them with additional soil.
Construction crews also excavate when they remove material from the ground. Workers slowly excavate subways tunnels using explosives to break up the rock and earth. Then the workers clear away the materials, hollowing out a tunnel as they go. It often takes a lot of time and effort to excavate. But most people would agree a new subway line is dynamite!