I'm in a tank...

I’m in a tank and i run across a *mine, and begin to roll into a shallow, but steep ditch. which way do I turn my **turret to prevent my tank from rolling?

*here, assume “an explosive device capable of rolling a modern tank”
**assume a 20mm barrel, and remember the counterweights to balance the weight of the barrel

left

dang it, i meant 20cm, but upon further thought that seems a tad large… just make it a standard tank barrel.

In short, you don’t. First, if a mine hits hard enough to roll a sixty ton tank, you will not be in any condition to take action. You will be a red paste on the interior walls. Second, and most importantly, a 20mm turret isn’t any great weight: most of them have a center of gravity essentially in the middle of the turret ring. You can’t shift your center of gravity by moving it, and there is no way a 20mm barrel is long enough to catch something, even if it were strong enough. Even a much larger gun, 105 or 120mm, will likely just catch or deform.