Steps to take backup of site collection
1) Open Central Administration. Go to ‘Backup and Restore’.
2) Under ‘Granular Backup’, click on ‘perform a site collection’.
3) Choose any site collection from the site collection list. Enter destination for the backup file. and click on ‘Start Backup’.
4) Once backup is finished, check if the backup file is created.
Steps to Restore site collection
1) Create a site collection.
2) Open Sharepoint 2010 Management shell.
3) Run the following powershell command.
Restore-SPSite -Identity http://sitecollectionurl -Path “filepath” -Force
This will successfully fill all the content in new site collection.