At first make sure that there is a mole in your garden and not a vole. You can figure this out by opening one of the piles. If it is reclosed within several minutes, or in a time up to six hours, you most likely have a vole in your garden.
Moles easily feel disturbed by noise, stench and concussion because of their good sense organs. We can take advantage of this and try to expel the mole through malodours or concussions.
With the following methods you can banish a mole:
Place odour carriers like sour milk, dog hair, dried peppermint, cloves of garlic, onion and elder leaves directly into the tunnels. To do this, carefully open the mole hill, dig in deeply the fragrance carrier and close the hole. These odour sources should be renewed weekly until no new pile is built.
Another option is to banish the mole with the help of sound waves. Take an empty glass bottle and place it skewed into the ground. The wind creates a sound which disturbs the mole. You also can use small wind turbines which create a squeaky sound.
If these actions do not help, it either is a vole or a very obstinate mole. In the latter case you should call a specialist which can establish a live trap. Private people should not do that.
In Germany, the mole is a protected species.