Snail Digging?

One of my mystery snails is acting very strangely, I really thought it was dead at one point but it kept moving around the tank so I figure it must still be alive. I have officiall seen signs of life so I know it's still alive but this morning it looked like it was digging a hole in the gravel. Is this normal? Should I be concerned?
 
quite normal for apple snails to do this.

maybe he/she thinks they'll to get to china eventually? lol!
 
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