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Many construction projects involve the digging of trenches and depressions by earth removal machinery. Trench shoring is the reinforcing of these trenches by the use of a metal or timber shoring system that prevents the sides of the trench from caving in. This is done not only to maintain the shape and usefulness of trenches, but to protect the lives of workers laboring inside them.
In construction, trenching is needed in almost every project. A trench is generally deeper than it is wide, and most are 15 feet (4.57 m) in width or less. Trenching is considered by many to be the most dangerous part of a construction job, so it is important for workers on the site to be able to be safe while working in a trench.
There are several types of trench shoring that are commonly used, depending on the dimensions of the trench and the kind of soil it is dug into. For narrow trenches, small aluminum hydraulic shores are placed between the sides of the trench. These shores resemble small ladders, and can easily be handled by one worker, and installed as fast as the trench is dug. Slightly different shores for narrow and deep excavations consist of corrugated aluminum panels separated by adjustable bars. These shores can weigh hundreds of pounds less than other devices used for shoring deep trenches.
Flat steel plates are often used for trench shoring when the trench is wide. These plates are held in place by steel screw jacks, which press outward against the sides, in the same way that a shower curtain rod works. At times, a trench will need to be reinforced with trench boxes. These are usually made of plywood, with metal reinforcing at the corners. Trench boxes cover not only the sides but also the bottom of the trench, and are most useful where it is important to maintain the integrity of all sides of the trench.
Trench shoring is crucial to every construction site because of the danger that would exist without it. A cubic yard of soil can weigh up to 3,000 lbs. (1,360 kg), which is enough to instantly kill a worker who gets trapped in a collapse. The increased use of trench shoring has led to a decrease in these types of fatalities, but being aware and following safety rules are still paramount.
Even in a properly shored trench, there are dangers. For example, a trench worker must be aware of what equipment is being used nearby. Fumes from construction equipment can easily settle into trenches as pose just as serious a hazard as a collapse would.