I'm looking for a book where the people live in some sort of communist community in a very deep ravine. It's so deep that they think the sun doesn't shine anymore. They have a lot of supplies to stay in the ravine for years. The story starts at a point that the resources/supplies are running low and one person starts to think what they should do next. Eventually the main character escapes from the ravine and finds that there are still people living outside of it.
The community in the ravine is very happy with the way they live there so most of them don't want to go outside of the city or leave the ravine. They have a very dictatorial mayor who tries to keep everyone inside the city. Most of them are left behind in the city.
As far as I can recall the main character is girl living with her grandma.
It has been several years ago since I read the book. And I think it was written for teenagers/young adults.
I read the book in Dutch, but it was a translated version. I got the book from the local library but they don't have it anymore and don't have old records of me (as in older then 5 years old).