This is a picture I finished recently
Please post your C&Cs
In general it looks good 
What doesn’t work well though is that pole on the left. It has been illuminated by the sun too much, thus sticking out and being an eyesore. It would have been ok if it had been a darker piece of wood with a complex texture.
You might want to put more emphasis on the tools instead.
Aligorith
I like mine shafts (one day I’ll do that animation!) and sunlit images. I agree with Aligorith that the foreground post is too dominant. In art-speak I’d say that the eye stops at this post and is prevented from travelling deeper into the picture.
Just turn that post around a little so that sunlit face isn’t toward the sun (just like the post at the front.)
The rocks on the floor are a little uniform in size and spacing. There are no small rocks at all. It’s like someone swept everything up then went back and put those hand-size rocks back in place. Also, the larger rocks leaning up against the walls seem to be almost exactly the same size and again they too are evenly spaced and leaning at the same angles. This is a mine, no janitors in here. Get in there and make a mess - like a good miner would!
Overall I like the image but ask yourself what the focal point (point of interest) is and if you think it is the most dominant thing in the picture? Currently it seems to be a battle between the foreground post and the sunset image. The bits in the middle seem secondary.
Update 1
Did some processing with irfanview here is the result
Please post your C&Cs
Same crits as before - but now the image is sharper :).
UPDATE 2
Did some more processing with the gimp
Please post your C&Cs
i liked the first one