It is fine that slug front within pipe is assumed to be hydraulic jump. But i am looking for some work in which its analysis in terms of forces and energy loss at slug front is provided.
[I never seen a research or an article on this issue, probably because it does not have industrial importance or application, I saw a master thesis in Utah State University (Logan) on the hydraulic jump in the pipes, it was experimental]
look at the culvert design manuals and experimental works on the culverts when downstream is submerged. That is hydraulically identical to your question. It is not the answer but it can be your start point. See U.S. Federal Highway Administration works on culverts or USACE.