Games : why are there vines over the entrance to Bthatdamz on skyrym elder scrools V

I am looking for the atherium shards for the key to the atherium forge and went to Bthardamz to search and after you go down the stairs where you can pull a lever and the spinning blades come out then i pulled the one for the bars to open the next room. But when I get to the next door there are vines covering the door. What do i do?