Many of you will have seen films in which a character steps on a mine and the mine does not detonate until the victim's weight is removed. Sometimes the mine clicks and waits for no apparent reason other than to allow Arnie to jump aside and shout a warning. Despite the tall tales of US ex-servicemen, there really is no such mine. Within the demining industry, the kind of mine that detonates when the soldier steps OFF it is referred to with contempt as the HSE mine. (Hollywood Special Effects mine). The pretence that a mine works in this way gives cinema an opportunity to dramatise an event that is so fast that it is not dramatic, just brutal. The fact that these mines are featured in films does not imply that they are real - anymore than a film about Superman proves he is real.
No mine ever recorded in any publication I have seen, or encountered by any person I have asked (and I have asked many) is activated when the soldier steps off the mine. Despite many tall-tales, there is no mine that would allow a buddy to slide a weighted plate under your foot or dig down and defuse it, so preventing you losing your foot.
A few booby trap switches are set for pressure release. A weight is placed on top of the switch before it is armed (mines and booby traps are armed by removing a pin, clip or cover-plate). If the weight is removed the device explodes. These are not mines, they are booby-traps, and still they would not allow you to step on them and only detonate when you stepped off. (See the MS3.)
The manufacture of a mine with the features of an HSE mine would be complicated, more expensive and more likely to fail. It would be counter-productive in military terms because it would give the opportunity
for a victim's comrades to run away and avoid the mine claiming more than one victim.
Further, it is my opinion (after discussion with many experienced demining people) that no mine could fail in a way that made it work like this. The same is true of improvised mines using manufactured fuzes and parts.
If you want to know more about mine mechanisms, there are a lot of information sources scattered around the web. A free online mine and UXO database (named ORDATA - now aka "CORD" ) is available at the James Madison University site.