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Excavation

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(Redirected from Excavated)
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Kobelco SK220LC Excavator
Excavation
is a method in which earthmoving machines remove dirt, soil, rocks, and other materials in order to create a trench, hole, pit, or foundation. Excavation, a process that commonly occurs in the construction, mining, and even sometimes agricultural industries, can be carried out in a number of ways by various machines such as excavators, trenchers, motor scrapers, wheel loaders, and more.

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[edit] History

Early excavation methods took place with primitive tools such as shovels or fork-like devices that required extensive manpower in order to excavate a hole of large proportions. These shovels were gradually enlarged to suit the excavation job. William Otis invented an excavator-type machine with an articulated arm and bucket in 1839. The shovel was mounted on a railway chassis and was capable only of a partial swing. Its movement, as such, was produced by steam power. The Otis shovel was originally built to aid in the construction of the railroad contract for Carmichael & Fairbanks.[1]

The excavator descended from the steam shovel. The first type to be used was the cable excavator, a machine that relied on a series of cables or wire ropes to lower the arm and bucket close to the earth to cut and extract dirt. The cables were pulled and hoisted in the preferred direction to collect and excavate a hole. As the cable excavator was costly, difficult to maneuver, and slow, other types of excavating machinery were sought out by the industry.

The answer was the hydraulic excavator. Hydraulics is a mechanical technology that enables oil or other liquids to produce movements between pistons and cylinders. Such technology creates a force or movement that is exerted to lead to an action such as digging.

Hydraulic excavators first appeared around in 1882 by British firm Sir W.G. Armstrong & Co. It was used for the construction of hull docks. Slow to make its way into the industry, hydraulic excavators began to gain popularity in the 1940s, particularly Carlo and Mario Bruneri’s wheeled version in 1948 in Turin, Italy. The use of hydraulics in an excavator improved the process of excavation. The wheeled prototype could move faster than the cable excavator, with none of the formers clumsy and awkward movement. It didn’t rely on the use of railroads, meaning it could be driven throughout the construction site. This expanded the number of digging applications for which the excavator could be used.[2]

Many other excavators derived from this, such as the mini excavator and the long reach excavator. Excavators were not confined to a single configuration. Some had features that shortened or elongated the arm, or increased or decreased the size of the bucket. The feet that moved the excavator could be tracked or tired. Many more features distinguished different types of excavators that were designed specifically for different applications. Their evolution, in fact, continues to grow.[3]

Similarly, other machinery can be used for the purpose of excavation. Contractors will utilize whatever is necessary to keep within cost constraints so long as it is proficient. Minor excavation projects that require not so much of a hole or pit but rather the pushing of dirt can be carried out by motor scrapers, backhoes, and wheel loaders. These types of machinery don't exactly pick up the dirt, but move it to a nearby location for backfill or foundation-laying purposes.

The type of excavation also determines the type of machinery that is to be utilized. In pipeline construction or trenching applications, contractors will use pipelayers or trenchers. These are machines that are able to dig deep, narrow, and long trenches in continuous excavation. Often times, a number of these machines are used in conjunction with one another.

The introduction of hydraulics has progressed mechanization to the point where any excavation project can be tackled with ease. Some of the most diverse and challenging excavation projects include the Kola Superdeep Borehole, the deepest excavation known to man. Other projects of notable mention are the Hoover Dam, and the Langeled Pipeline.

[edit] Type

Machinery capable of advancing the excavation procedure include:

Excavation is carried out for a number of applications including:

[edit] Process

What makes the excavation process possible is the use of a tool or attachment shaped like a shovel or bucket. Today, these buckets are mechanically inclined and can be operated by the touch of a button by an operator in a machine's cab. Excavation takes place when the bucket or shovel-like tool penetrates the earth, collects it, and disposes of it either somewhere else on the site or in an ADT or dump truck, with which it is further transported.

The articulated arm of a hydraulic excavator bends much like a human arm (at the elbow and wrist) and scoops up earth with its buckets. Other machinery relies on a tool such as a dozer blade to scrape and propel earth from its natural state.

Excavation commonly occurs in many, if not all, construction applications, as well as some agricultural and mining applications. In agriculture, a variety of tools such as air drills and harvesters are used to till the soil and drill small holes into the earth for the purpose of reaping and harvesting. In mining, excavation can occur in the construction of an open-pit mine, in which the overburden of the pit has to be removed by stripping shovels and draglines in order to extract valuable materials. Similarly, in underground mines, minor excavation or drilling of harder substances such as rock can occur to either prepare for the mining excavation or to create stopes.[4]

[edit] References


  1. Haddock, Keith. Bucyrus: Making the Earth Move for 125 Years. Motorbooks: 2005.
  2. Haddock, Keith. The Earthmover Encylopedia. Motorbooks: St. Paul, 2002. 225-263.
  3. The Mechanism of a Hydraulic Excavator, Everything About Construction Equipment, 2008-08-24.
  4. Haddock, Keith. Bucyrus: Making the Earth Move for 125 Years. Motorbooks: 2005.