Mine

I

Introduction

Mine, in warfare, explosive device used on land or at sea, designed to destroy or disable enemy troops, ships, and vehicles such as tanks. Mines also serve to impede the progress of advancing troops and to render terrain, shipping lanes, and harbours impassable. A minefield is a terrain containing numerous buried mines. In the American Civil War and World War I, networks of tunnels were dug under enemy positions and filled with explosives. From this practice, mining came to refer to the placement of an encased explosive device. Defence experts in the United Kingdom have listed as many as 500 types of mine, which kill and injure by blast—usually set off by a person’s foot—or by fragmentation, the Claymore anti-personnel mine being the prime example.

II

Landmines

An encased explosive device that is concealed below the surface of the ground is called a landmine. Made of metal, plastic, glass, or wood, it is detonated in a number of ways, such as by disturbing a trip-wire attachment to the mine or by a delayed-action mechanism. The explosive most commonly used in landmines is trinitrotoluene (TNT).

Anti-tank mines have an explosive charge of from 2.7 to 5.4 kg (6 to 12 lb) of TNT and are used to destroy vehicles passing over them. Anti-personnel mines have a normal charge of from 0.1 to 1.8 kg (‚ to 4 lb) and are designed to kill or injure foot soldiers. In World War II the Germans used an anti-personnel mine known as the Bouncing Betty, which was activated by a trip wire that caused the mine to fly some 30 to 60 cm (about 12 to 24 in) into the air before exploding. During the Korean War, landmines attached to a complicated network of trip wires were widely used to protect defensive positions.

In the Vietnam War the Claymore mine came into general use. Designed to kill by spraying high-speed fragments at the victim, Claymores, small and light, are made of plastic, contain a high-explosive substance and 700 steel balls each weighing 150 g (0.3 lb) that can be aimed in any direction, with a range of 76 m (250 ft). The Claymore can be pushed into the ground or hung from trees, about 60 to 90 cm (24 to 36 in) off the ground. A trip wire sets off the charge.

III

Submarine Mines

Mines can also be used in areas of water. Submarine mines are mines that float on or just below the surface of the water. Such mines may be anchored to the ocean bottom by a cable or set adrift to follow determined ocean or waterway currents. They explode on contact with the hull of a vessel, or sometimes through a magnetic mechanism. For protection against magnetic mines, the hull of a vessel can be encircled with electric cables called degaussing belts, that reduce the vessel’s magnetic field. The acoustic mine, which is drawn to the noise from the propellers of a passing ship, is likewise countered by a noisemaker towed behind the ship.

Mines may be put in place at sea by specially equipped minelaying ships, by aircraft that parachute the mines into the sea, or by submarines that eject cable or bottom mines. Areas of water infested with mines are also known as minefields. During wartime, mines are often used in harbours as a defence against submarines.

IV

Mine Detection

A

Landmine Detection

Detection and clearance teams face huge problems requiring new technologies in order to clear the world’s minefields and allow the redevelopment of former war zones. In 1993 UN personnel removed 80,000 mines, but some 2.5 million per year are still being laid. Land minesweeping devices resemble the metal detectors used by treasure hunters. In World War II, minefields were sometimes cleared by tanks. When detected, the mines are carefully uncovered and then disarmed by inserting a key-like device into the hole from which the pin has been removed. Automatic mine detectors attached to vehicles indicate the presence of hidden metal mines, but mines made of plastic or wood are difficult to detect.

Modern cheap plastic mines can escape discovery by mine detectors which detect mainly metal, although small amounts of metal are normally contained in the mine’s trigger mechanism. Metal detectors also respond to metal debris on former battlefields, with false alarms often the result. In addition, detected mines are usually blown up on the spot, creating yet more metal debris.

The highly dangerous operation of mine clearance still relies on simplistic methods of basic observation and detection using probe rods and metal detectors. No detection method is as yet capable of spotting every mine, and many new techniques and equipment are still under experimentation. These include the use of millimetre-wave cameras to spot objects which show up as darker than the background. Surface foliage, humidity levels, and soil types all influence the rate of detection (plastic mines can resemble wet soil) and research is being conducted into how different forms of radiation travel through soil. Work is continuing to find a combination of sensors using various frequencies, as well as airborne radars to map the edges of minefields, and ways to sense the chemical signature of mine explosives.

Mapping the size of a minefield is but one of the great difficulties involved at the start of a clearing operation. Many factors prevent successful detection, such as the similarity of the background’s appearance and temperature. Infrared imaging, airborne synthetic aperture radar (SAR), and ultra-wide band radar are aimed at mapping minefields and detecting plastic mines. At present, SAR works like normal radar in that it sends out radio pulses that are bounced off objects on the ground, but is also capable of combining image data to produce two-dimensional pictures of an observed area; computer programs are applied to creating radar image patterns.