The following assumes you have a Host Named Site Collection.
backup-spsite http://oilshop.beaversoil.com -Path e:\MyServerPath\MyFilename.bak -UseSQLSnapShot -force
Notice nothing special needs to be done in regards to the host named site collection when performing the backup.
Restore-SPSite http://oilshop.beaversoil.com -Path \\file_server\share\site_name.bak -HostHeaderWebApplication http://server_name.beaversoil.com
Notice how the actual web application is referenced, this is key