Dig Like a Mole (うまった道を行く, Umatta Michi o Yuku, lit. Go Along the Buried Road) is an event in Tomba!.
Wait until the miner has dug the tunnel.
In the Underground Maze, talk to the miner that is digging a tunnel to activate the event.
For them to finish the tunnels, Tomba must defeat all the seven Evil Pigs. When all of them are defeated, head back to the place where the miner was found earlier to clear the event.