Here's why:
* Mines are designed to explode. Unlike some traps, mines are meant to detonate upon contact. They are not designed to be deactivated.
* There is no in-game mechanism. Fallout 3 doesn't provide any tools or options to disarm mines.
Here are your options when encountering a mine:
* Avoid it: If possible, carefully move around the mine or find another route.
* Use V.A.T.S.: In V.A.T.S. mode, you can aim at the mine and potentially shoot it before it explodes. However, this is risky as even a near miss can trigger the mine.
* Throw something at it: You can try to throw a grenade or other object at the mine in the hopes of triggering its detonation remotely. Be very cautious doing this!
Important Note: It's best to avoid mines entirely in Fallout 3. They are a dangerous hazard and are designed to be difficult to deal with.