Dud mine explosion
From Worms Knowledge Base
Dud mines can be detonated, although the conditions are rather strange. In Worms Armageddon the 220.127.116.11 Beta update removed the ability to detonate dud mines. So in earlier versions or in Worms World Party, the mines would explode if the mine was within one pixel of the worm's origin, and was also present there during the frame where it checks for nearby worms (every 1/5th of a second). This is most easily achieved by having the mine bounce when near the worm's origin.
The most common way this was achieved was to hit the mine with a baseball bat and then backflip, as this gave the mine a speed large enough to "jump" inside the jumping worm's collision mask. Another method was to have a worm land exactly vertically on the mine when on a Jet Pack, which would cause the mine to bounce, although obviously doing this hurts your own worm. It's also fairly easy to accomplish this by drilling a hole (with the Pneumatic Drill) and having the dud mine bounce in as you're drilling it; it's quite common that the mine would bounce close enough to the worm's center to detonate, making it seem like it was "damaged" by the drill.
The way dud mines originally worked was that the mine's activation range was reduced to 0 when it turned into a dud, the theory being that no worm could get close enough to activate it. Unfortunately, it was possible as the activation area became one pixel big, so it was fixed by reducing the activation range further to -1.
The ability to detonate dud mines is planned to be re-introduced to Worms Armageddon, but only when a more suitable and sensible reason for detonation is decided.
Dud mine detonation in Worms 2 is an intentional feature, on the other hand. Dud mines explode the first time they hit the ground after being hit with a Baseball Bat or Fire Punch.