How Landmines Work

­Landmines are easy to make, cheap, and effective weapons that can be deployed easily over large areas to prevent enemy movements. Mines are typically placed in the ground by hand, but there are also mechanical minelayers that can plow the earth and drop and bury mines at specific intervals.

­Mines are often laid in groups, called minefields, and are designed to prevent the enemy fro­m passing through a certain area, or sometimes to force an enemy through a particular area. An army will also use landmines to slow an enemy until reinforcements can arrive. While more than 350 var­ieties of mines exist, they can be broken into two categories:

The basic function of both of these types of landmines is the same, but there are a couple of key differences between them. Anti-tank mines are typically larger and contain several times more explosive material than anti-personnel mines. There is enough explosive in an anti-tank mine to destroy a tank or truck, as well as kill soldiers or civilians in or around the vehicle.

Additionally, more pressure is usually required for an anti-tank mine to detonate. Most of these mines are found on roads, bridges and large clearances where tanks may travel. In the next two sections, you will get a closer look at a few landmines and the parts that make them work.

Anti-personnel landmines are designed specifically to reroute or push back foot soldiers from a given geographic area. These mines can kill or disable their victims, and are activated by direct pressure (such as contact with a person), tripwire, or remote detonation. There are also smart mines, which automatically deactivate themselves after a certain amount of time. These are the most common types of mines currently used by the U.S. military.

Anti-personnel mines fit into three basic categories:

There are several-hundred different kinds of anti-personnel mines in use by many countries. For the purposes of this article, we have chosen two landmines developed by the United States military that demonstrate the varying characteristics of landmines. The first landmine, the M14, is a pressure-operated blast mine. We also examine the M16 bounding/fragmentation landmine.

M14 Blast Mine

The M14 is a small, cylindrical, plastic-bodied blast mine. It is just 1.57 inches (40 mm) tall and 2.2 inches (56 mm) in diameter. It was originally developed and used by the United States in the 1950s, but it has been used and copied by many nations around the world. This particular anti-personnel mine contains only a small amount of explosive, about 31 grams of Tetryl. It is designed to kill people in close proximity.

The M14 is initially equipped with a U-shaped safety clip, which is fitted around the pressure plate. In order to activate the M14, the safety clip is removed and the pressure plate is rotated from its safety position to its armed position. The letters A (armed) and S (safety) are embossed on the pressure plate. Soldiers simply align an arrow with the A to arm the mine.

Once it is armed, any pressure of at least 19.8 pounds (9 kg) can cause the mine to detonate. When the proper amount of pressure is applied it pushes down on the Belleville spring underneath the pressure plate. This spring pushes the firing pin down on to the detonator, which ignites the main charge of Tetryl explosive.

M16 Bounding/Fragmentation Mine

Bounding mines fire up out of the ground and then explode. The M16 is made of three main parts: a mine fuse, a propelling charge to lift the mine, and a projectile contained in a cast-iron housing. It is 7.83 inches (199 mm) tall and 5.24 inches (133 mm) in diameter. The M16 mine contains about 1.15 pounds (521 grams) of trinitrotoluene (TNT) explosive.

The fuse extends through the center of the mine to the bottom, where the propelling charge is located. To arm the mine, a safety pin is removed from the striker on top of the fuse. There are three prongs located on top of the fuse, connected to a spring-loaded wedge. The fuse encloses a percussion cap, a delay element and a black-powder charge.

The M16 can be detonated in two ways: by applying pressure or by pulling the spring-loaded release pin. Either method causes the pin to pull out of the fuse, releasing the striker and igniting the percussion cap. The percussion cap fires a delay element in the fuse, and the detonator ignites the black powder in the fuse. The mine flies upward to about 1.2 meters; the main charge then detonates and releases a shower of metal fragments.

When it comes to developing new military weaponry, countries try to keep up with the developments of other countries. The development of tanks during World War I led to anti-tank mines, and anti-personnel mines were developed to prevent enemy armies from moving anti-tank mines.

Anti-tank mines are very similar to their anti-personnel cousins, but are much larger. These mines are pressure activated, but are typically designed so that the footstep of a person won't detonate them. Most anti vehicle mines require an applied pressure of 348.33 pounds (158 kg) to 745.16 pounds (338 kg) in order to detonate. Let's take a closer look at one of these anti-tank mines.

M15 Pressure-operated Blast Mine

All anti-tank mines are blast mines, because the goal of the anti-tank mine is to destroy the tank's tracks and as much of its body as possible. The M15 is a circular, steel anti-tank mine that contains a main charge of TNT. It has a diameter of 13.27 inches (337 mm) and a height of 4.92 inches (125 mm). The main component of the M15 is the 22.82 pounds (10.35 kg) of Composition B explosive. Composition B is a mix of TNT and cyclotrimethylene trinitramine (RDX).

The M15 is armed by rotating the arming switch so that it is set atop the head of the fuse. The cylindrical fuse is made of iron and is attached to the pressure plate by a copper cover. As a tank rolls over the mine, it pushes down on the pressure plate. Underneath the pressure plate is a Belleville spring with a firing pin affixed to its underside. The firing pin is driven down into the detonator, which detonates and fires the M120 booster charge beneath the fuse, which then sets off the main charge.

Landmines can remain active more than 50 years after they are planted in the ground. For this reason, there has been a growing effort to create a mine-free world in recent decades. To do this, humanitarian aid must first locate the millions of landmines that are still buried in dozens of countries around the world. Finding these landmines is a continuing challenge, as most minefields are unmarked. And those that are marked can take years to de-mine.

Landmine detection is a slow, methodical process due to the danger involved in locating landmines. While location technology is improving, the following conventional techniques are still relied on heavily:

Scientists at Ohio State University are developing a new ground-penetrating radar (GPR) device that may be more effective in locating and disarming landmines. A GPR device focuses radar energy just below the ground and just a few feet in front of the user, according to researchers. The device ignores signals that bounce back from the surface and uses specially designed software to make buried objects shine brighter in the radar image.

Once a landmine is detected, the GPR device shoots two chemical agents into the ground to deactivate it. One agent solidifies the triggering mechanism along with surrounding soil, allowing soldiers to cross the ground. The second chemical agent then solidifies the mine and soil permanently. The mine can then be shoveled out and destroyed.

When there is not a lot of time for an army to clear a minefield, military forces employ several kinds of mine-clearing machines to clear out or detonate mines. Mine-clearing machines use one of three techniques, including flailing chains to beat the ground, rollers to roll over and detonate mines, and rakes or blades to plow through the minefields, pushing the mines to the side. Let's look at a few of these machines:

New mines are laid at a rate 25 times faster than they are being cleared. New technologies will make it easier to find and locate mines, but they can't prevent their placement. As long as nations continue to use landmines, and no mine ban treaty is implemented, these devices will be a danger for civilians as well as soldiers.