PowerShell script to set a large number of SharePoint 2013 site collections to "No Access" lock status

I have several hundred sites on my SharePoint 2013 farm that I need to set to "No Access" by locking the site collection.  What I would like to do, is use a PowerShell script to read the list of URL's from a text file, loop through each one, and lock the site collection.  This is what I have so far, but need some assistance on getting it completed:

Add-PSSnapin Microsoft.SharePoint.PowerShell -erroraction SilentlyContinue
 
$Sites = Get-Content -Path e:\scripts\SitesToLock.txt
 
ForEach ($site in $Sites) 
{
  Set-SPSite -Identity $site.Url -LockState "NoAccess" }

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