Why are some parts of the Trans-Alaska oil pipeline raised on stilts?

Hi Talia,

Before we look into the answer, we should know that in many parts of Alaska, the temparature remains below zero throughout the year and so the ground remains frozen solid. Such places are called permafrost.

So one citable reason for elevating parts (in places of permafrost) of the Trans-Alaskan oil pipeline using supporting members is to prevent the frozen ground from warming up (also called thawing) due to the flow of hot oil through the pipeline. If the ground gets heated, the ground might 'melt' ;ie, the physical properties of the ground might change and become more fluid and the pipeline might sink if it was buried underground. This might cause a breakage in the pipeline and even cause a spill which is not a good scenario. So these pipelines are kept elevated above ground using refrigerated supporting members.

In order to prevent the hot oil from melting the permafrost, more than half the pipeline is raised on stilts.

To keep the permafrost from melting.