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One principal difficulty land mine clearance must cope with is the diversity of mines. Land mines can target either vehicles, principally tanks, or people. I will concentrate exclusively antipersonnel mines, since they represent the overwhelming majority. Further, anti-tank mines are generally designed so that the weight of a person will not detonate them, and being larger and heavier than antipersonnel mines, are correspondingly easier to locate. In fact, a frequent military application of antipersonnel mines is to deter and impede anti-tank mine clearance.

Of the more than 700 types of known antipersonnel mines, the most common is the blast mine. It is buried at a shallow depth in the soil, rarely deeper than 10 cm, and triggered by the pressure of a footstep. The trigger requires a minimum weight of about 5 kg so as not to be set off by small animals, but many of these mines are crudely constructed and deteriorate in the ground so one cannot predict the conditions which will cause them to explode. The square wooden box PMD-6, encountered frequently in Cambodia, can spontaneously explode or be triggered by a very slight pressure as the wood rots and components shift.

A blast mine typically injures only the person who steps on it, resulting in the amputation of a leg. Since many proposals for mine clearance involve means to detonate mines in place, I'd like to give you a sense of the magnitude of the explosions we're talking about.

At this point in the session I played a video of detonations of various amounts of high explosive conducted at the Swiss Army proving ground at Thun, Switzerland on 20th September 1996 in order to measure blast, sand and gravel dispersal effects, and test attenuation of these by various water-filled devices. The movies were made in 1996; due to Web bandwidth limitations at the time, they were made as 192×144 pixel thumbnails. No larger versions are available. The perturbations seen on the videos are due to the effects of the shock wave on the tape transit mechanism of the analogue camcorder used to record them.