Do they dig for fun? (Rankins Dragons)

I just wondered because since my little girls (now just over a year old) reached 6-8 months I have given them a deepish dish full of topsoil in case they wanted to lay eggs. One of them today was playing around in there and digging frantically for some 10 minutes making a hollow in the dish. I checked when she got out, but no eggs. So basically I wondered if they will dig anyway (given the opportunity - I know my sav will but he's a monitor) even if there are no eggs. I'm worried in case she gets egg-bound as she hasn't laid them. Also wonder how deep the soil should be (bearing in mind the Rankins are 1/3 the size of beardies and she's only about 10 inches long).

Any insight into egg-laying greatly appreciated :)

I'm no expert, but Pete, my male BD digs a LOT too... I think its normal that they dig a lot, but I really have no clue about the eggs. ^^;;