Can I get past the rocks in the Jarn mines?
Solution 1:
No.
It is not possible to get past them by any conventional means, and there is no playable area or easter egg behind them. It may be possible to blast yourself over top of the area with [ARSE] mines, but the level simply curves around to where the tunnel exit would presumably be.
Source: 70 hours played including the "Sherlock Holmes" achievement - Find all secret areas in the game.
It isn't a secret area, and there is no way to get past it, similar to the log blocking the road in Chapter 3.