My 1 year old Great Dane is home alone during the day – what can I do to avoid her tearing up stuff?

My great dane is home alone for most of the day as we work full time. We got her a dog companion so she doesn't feel so alone! Unfortunately, she still seems to feel abandonned. They stay in a 10 x 10 kennel in our garage! We can't leave the pillows in it as she will shred them to pieces! Recently we invested in some linoleum so they are not on the cement and she even managed to tear a huge hole in it!! What can I do to stop that?
We can not leave her outside all day as she will dig in the yard and even has dug out bushes and small trees. We play with her for 15 minutes or so in the morning before we leave! She has tore up any rug we put in there so far!