Here's a script to replicate a landmine. I tested it with the default media ww2/furniturea/itemc (which looks sort of landmine like).
Set the entity to static=no, strength to 20 and explodable? = yes
The mine is triggers when you get close enough and won't explode until you step away from it.
I hope that's what you were looking for?
;Artificial Intelligence Script
;Header
desc = landmine
;by the scene commander
;Triggers
:state=0:state=1
:state=1,plrdistwithin=50:state=2
:state=2,plrdistfurther=70:subhealth=5000,state=3
;End of Script