Share Point Site Collecton Backup/Re-Store & Remove/Delete using power shell.

   Open  "SharePoint Management Shell" by click on Start > Program > Microsoft SharePoint 2013 > and then click SharePoint Management Shell. 

Backup

Backup-spsite  -Identity sitecollectionname  -path location to store the back up

Restore

Restore-SPSite -Identity sitecollectionname   -path path location of stored back up file

Remove site collection

Remove-SPSite -Identity sitecollectionname