Common Alias for Dav Users

I'm trying to configure a Dav server, that has user directories and
each directory has access to a common share.

/(Root)
/User1
/User1/common
/User2/
/User2/common

I have the following configuration, but I don't know how to implement
the common folder.

<VirtualHost dav.server.net:80>
ServerName dav.server.net
<Directory /mnt/common>
Dav ON
AllowOverride None
<Limit PUT POST DELETE PROPFIND PROPPATCH MKCOL COPY MOVE LOCK
UNLOCK>
Require valid-user
</Limit>
</Directory>

DocumentRoot /var/www/dav
<Directory /var/www/dav>
Dav ON
AuthType Digest
AuthName "DavAuth"
AuthDigestDomain "/"
AuthDigestFile /var/www/.digest_pw
Require valid-user
AllowOverride None
Options None
<Limit PUT POST DELETE PROPFIND PROPPATCH MKCOL COPY MOVE LOCK
UNLOCK>
Require valid-user
</Limit>
</Directory>
<Location /user1>
DAVDepthInfinity On
<Limit PUT POST DELETE PROPPATCH MKCOL COPY MOVE LOCK UNLOCK
PROPFIND>
Require user user1
</Limit>
</Location>
<Location /user2>
DAVDepthInfinity On
<Limit PUT POST DELETE PROPPATCH MKCOL COPY MOVE LOCK UNLOCK
PROPFIND>
Require user user2
</Limit>
</Location>
</VirtualHost>