Insulated heat pipes, gravel pads, and __________ are used to build on top of permafrost.
a. shaved sod chips
b. rubber pads
c. ice blocks
d. wood piles
The answer would be letter D. Insulated heated pipes, gravel pads, and wood piles are being used to build on top of the permafrost. Permafrost is a ground that being frozen at or below zero of water in two years or more.
