Gravel mines, also called Button mines, were small United States made air-dropped

anti-personnel mine Anti-personnel mines are a form of mine designed for use against humans, as opposed to anti-tank mines, which are designed for use against vehicles. Anti-personnel mines may be classified into blast mines or fragmentation mines; the latter may ...

s. They were used extensively during the

Vietnam War The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...

as part of the

McNamara Line The McNamara Line, an operational strategy employed by the United States in 1966–1968 during the Vietnam War, aimed to prevent infiltration of South Vietnam by NVA forces from North Vietnam and Laos. Physically, the McNamara Line ran across So ...

. They were also used as a rapid-deployment area denial expedient, to provide a barrier during combat search and rescue (CSAR) operations between downed pilots or other endangered units and infantry threats.

General information

Components

The mines consisted of a small green or brown

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the ...

fabric pouch filled with

lead(II) azide Lead(II) azide is an inorganic compound. More so than other azides, is explosive. It is used in detonators to initiate secondary explosives. In a commercially usable form, it is a white to buff powder. Preparation and handling Lead(II) azide i ...

and 30 grams of coarse ground glass between two sheets of plastic. No

fuse Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protect ...

was required because the explosive became shock-sensitive after dispersal, i.e. able to be detonated without a fuse on contact. The explosive lumps came in wedge or cubed shapes and their

plasticizers A plasticizer ( UK: plasticiser) is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture. Plasticiz ...

evaporated after three to eight minutes exposure to air. To allow them to be handled and dropped from the air, the mines were

phlegmatized A phlegmatized explosive is an explosive that has had an agent (a phlegmatizer) added to stabilize or desensitize it. Phlegmatizing usually improves the handling properties of an explosive (e.g. when munitions are filled in factories. Alfred N ...

with

Freon 113 1,1,2-Trichloro-1,2,2-trifluoroethane, also called trichlorotrifluoroethane or CFC-113, is a chlorofluorocarbon. It has the formula . This colorless, volatile liquid is a versatile solvent. Atmospheric reactions CFC-113 is a very unreactive chl ...

, in which they were stored soaked. Once released from their container, the Freon would evaporate in between 3 and 8 minutes, thereby arming the mines. The mines varied in size, from simple warning bomblets (Button mines), whose detonation was to be picked up by air dropped acoustic sensors and relayed to a central control center , through to larger mines, while not powerful enough to kill a person outright, they were capable of wounding anyone stepping on it. The larger mines were fitted with a two tablet chemical system to gradually render the explosive inert, although the reliability of this mechanism was never gauged accurately.

Usage

The mines were also used by the U.S. during the

Battle of Khe Sanh The Battle of Khe Sanh (21 January – 9 July 1968) was conducted in the Khe Sanh area of northwestern Quảng Trị Province, Republic of Vietnam (South Vietnam), during the Vietnam War. The main US forces defending Khe Sanh Combat Base (KSCB) ...

; however, a U.S. Air Force history described them as being "little more than a nuisance," due to the

Viet Cong , , war = the Vietnam War , image = FNL Flag.svg , caption = The flag of the Viet Cong, adopted in 1960, is a variation on the flag of North Vietnam. Sometimes the lower stripe was green. , active ...

clearing the gravel mine fields by using teams of oxen that dragged logs over them and to the mines themselves becoming inert after a short time.

Manufacture

A total of 37 million gravel mines were produced between 1967 and 1968, though mines were produced into 1970.

Specifications

The mines were typically deployed from SUU-41A/A and SUU-41B/A dispensers, with the dispensers packed into cluster bomb units with between 12 and 16 dispensers in each cluster bomb. A single bomb could contain between 1,470 and 7,500 mines. The bombs could be dropped from aircraft at between 60 and 6000 meters and at speeds of 370 km/h to 1300 km/h. The dispensers would burst at an altitude of between 200 and 300 meters, scattering the mines.

Dispenser configurations

* SUU-41A/A ** 150 × XM41E1 per dispenser (10 dispensers per CBU) ** 750 × XM40E5 per dispenser (10 dispensers per CBU) ** 650 × XM40E5 and 48x XM44 per dispenser (10 dispensers per CBU) * SUU-41B/A ** 150 × XM65 per dispenser (10 dispensers per CBU)

References

* * {{reflist Anti-personnel mines Submunitions