Yup, I agree with that. But we are talking about 2 different things. You're talking about frost heaves causing a shift in conduits emerging from underground. I am talking about the change in length of a conduit due to thermal variation.
For instance, anywhere in the US where a 20' PVC conduit length is outdoors and above grade, there should be an expansion joint along with the proper PVC supports that allow the conduit to slide within it. However, the same steel or aluminum conduit run would not require the expansion joint. I see these expansion joints missing all the time and as a result, I see a lot of ugly sagging runs, couplings pulled apart (shrinkage) and broken out junction boxes (expansion).
In fact, even when burying PVC care must be taken. If the air temperature is significantly hotter or colder than the ground temperature, then there can be problems that occur once buried. If it's very hot out and conduit has been laying in the sun, it is fully expanded. Once glued together and buried, it cools and shrinks and the couplings can pull apart if they are long runs.
