i end my topic and locked it .
when try to move it to Archival get this error "You are not allowed to move topics there."
I may be wrong but only Mods have the access to move threads into the trash-can.You can always try a workaround that is,use 'Report to Moderator' option with a comment why would you want the thread to be deleted.This is just a rough guess,actually I could be right.