Cant' knock over shelf at beginning

[gakido]

I can't push over the metal shelf which is blocking the tunnel entrance at the very beginning of the mine. I use the same mouse button I used to pick up the rock to smash the ice on the hatch, I can pull the lid off the crate with the flare in it, but I can't get this shelf to move. Is there a trick to it? Do I have to stand in a certain location when I push on it, or is there some detail I'm missing?

Thanks in advance.