For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Morning in the camp – from when Shukhov wakes up till the gangs arrive at the worksite.
The workday – the entire period at the worksite until the gangs march back to camp.
Nighttime in the camp – from the arrival back at camp that night until the end of the book.