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A blasting mat is a
mat usually made of sliced-up rubber tires bound together with ropes, cables or chains. They are used during
rock blasting
Drilling and blasting is the controlled use of explosives and other methods, such as gas pressure blasting pyrotechnics, to break rock for excavation. It is practiced most often in mining, quarrying and civil engineering such as dam, tunnel o ...
to contain the blast, prevent flying rocks and suppress dust.
Use
Blasting mats are used when explosives are detonated in places such as
quarries
A quarry is a type of open-pit mine in which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some jurisdictions to reduce their environ ...
or
construction
Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and com ...
sites. The mats are placed over the blasting area to contain the blast, suppress noise
and dust as well as prevent high velocity rock fragments called fly rock (or flyrock) from damaging structures,
people or the
environment
Environment most often refers to:
__NOTOC__
* Natural environment, all living and non-living things occurring naturally
* Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...
in proximity to the blast site. The amount of fly rock can be reduced by proper drilling in the bedrock for the explosives, but in practice it is hard to avoid.
Mats can be used singly or in layers depending on the size of the blast charge, the type of mat and the amount of protection needed.
They can be used horizontally on the ground or vertically hanging from cranes or attached to structures. In the vertical capacity the mats are sometimes referred to as blasting curtains. When used in blasting tunnels the mats can be placed in patterns designed to let the mats stabilize each other and to direct the discharge from the explosion out of the tunnel.
To prevent mats from being displaced by the explosion, they can be covered with layers of soil or anchored to the ground.
Anchoring the mats is also essential when the blasting is done on an incline where the mats may slide down from the rock face.
Blasting mats are often used in combination with blasting blankets as an additional layer over the mats. The blankets are larger than the mats designed to retain the fragments that have managed to pass through the mat. Blasting blankets are used for both horizontal and vertical blasting.
Blasting blankets consist of a fine-mesh strong net or industrial felt from paper mills.
Both mats and blankets are designed to let air and gasses from the explosion pass through the cover and retain fragments.
Knowledge of the proper use of blasting mats is required in order to obtain a
blaster's certificate issued by organizations such as the
WorkSafeBC
The Workers' Compensation Board of British Columbia, operating as WorkSafeBC, is a statutory agency that came into existence in 1917, after the provincial legislature put into force legislation passed in 1902. This legislation is known as the '' ...
.
Blasting mats made from used tires can serve a double purpose as road stabilizers, or road surface, in locations where roads leading to the blasting site are unstable or nonexistent, or in areas where the surface needs to be protected from heavy machinery.
Materials
A number of materials are used for making blasting mats and new materials with different properties are constantly being introduced into this field.
The most common materials are strips of
old tires held together by steel cables, mats woven from
manila rope
Manila rope is a type of rope made from manila hemp.
Manila hemp is a type of fiber obtained from the leaves of the abacá
Abacá ( ; fil, Abaka ), binomial name ''Musa textilis'', is a species of banana native to the Philippines, grow ...
or
wire cables, logs or
conveyor belt
A conveyor belt is the carrying medium of a belt conveyor system (often shortened to belt conveyor). A belt conveyor system is one of many types of conveyor systems. A belt conveyor system consists of two or more pulleys (sometimes referred to ...
s.
Layers of
wire netting
Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm
A wire is a flexible strand of metal.
Wire is co ...
can also be used.
Several methods of assembling a blasting mat are patented.
Blasting mats made from rope woven on wires were first used during the construction of the
IRT Third Avenue Line
The IRT Third Avenue Line, commonly known as the Third Avenue Elevated, Third Avenue El, or Bronx El, was an elevated railway in Manhattan and the Bronx, New York City. Originally operated by the New York Elevated Railway, an independent railwa ...
in New York City in the early 1900s. They were used to protect the surrounding buildings and were favored since they prevented fly rock but vented gasses.
Mats made from recycled tires can be fashioned in a number of ways depending on how the tires are cut. Some examples are tread mats, sidewall mats and mats from non-flattened sections of tires.
File:Tread mat.jpg, Tread mat
File:Sidewall mat.jpg, Sidewall mat
File:Quarter tire mat.jpg, Quarter tire mat
Manufacturing
The manufacturing of blasting mats is integrated with the mining industry and many companies specialize in making mats, especially those made from recycled tires.
Military use
When charges are used to dig
foxholes, an improvised blasting mat made from whole tires tied together with rope to reduce noise and fly rock, is recommended in the ''A Soldiers Handbook'' (United States). A
tarp may also be used as a blasting blanket.
Accidents
Over the years, a number of incidents with fatal outcomes have been caused by fly rock. In most of these, blasting mats were not used or they were placed over the blasting face in an incorrect manner. Such an incident occurred in August 2015, in
Cape Ray, Newfoundland and Labrador
Cape Ray is a local service district and designated place in the Canadian province of Newfoundland and Labrador. It is on the southwest coast of the island of Newfoundland.
History
Cape Ray, the cape located near the community was the term ...
when a fly rock travelled about from the blast site
and crashed through the kitchen ceiling of a nearby house.
Although designed to prevent accidents, as blasting mats weigh between , they have also caused injuries when falling on workers on construction sites.
Blasting mats must be thoroughly inspected before each use to ensure there are no blown out segments or broken cables, by a blaster. Blasting mats will deteriorate with each use to the point where they become ineffective for their intended purpose. Only trained experienced and adequately supervised crews should be used in the placement of these devices over a loaded shot. A common complaint is accidental breakage of bus wires, leg wires or pinching off the non electric tubes that may result in the misfire of the shot.
References
{{reflist, 30em
Explosives engineering
Explosion protection
Military engineering
Mining engineering
Mining equipment
Mine safety
Vehicle recycling
Improvisation
Recycling by product