Soviet BTM Trenching Machine. It is a T-54/55 chasis based trench digger. It has the T-54/55 chasis witha truck cab on top and a large trench digging wheel on back that is in the stowed position in the photo. It swings down and out and cuts a trench behind the vehicle. Here is another photo of a similar vehicle:
There was a whole family of engineer vehicles built on the T-54/55 chasis with a truck cab on top. Check here for more varieties and pics.
Soviet engineer vehicles