Hill Climb

OK, todays picture is related to yesterdays. During lunch I decided to go check out how they caterpillar truck was able to get onto the top of the building. So I went to the back side and I saw the truck on a pile of rocks. Turns out the truck starts destroying one side of the building then the falling rubble creates a sort of a hill which the truck climbs on. The truck goes higher and destroys the top floors until another hill is formed and the truck climbs even higher. I doubt this is a safe practice since the rubble is very unstable and the truck not very easy to control. But, I guess its a cheap solution and thats why they use it.