Since the 1.10 update, burying or digging up stashes with the shovel causes it to quickly be damaged, in previous patches no damage was done to the shovel for these actions and now digging only 10 times takes a new shovel to badly damaged.
There is nothing in the patch notes about this change, so I am assuming it is unintentional. If the change is intentional it is very harsh and needs to have the damage done to the shovel reduced by a large factor as you should be able to dig a lot more than 10 times before almost ruining a brand new shovel.