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construction work that includes soil excavation (extraction), transportation, and placing of the soil in a predetermined location. (In some cases the stowage operation is accompanied by leveling and packing down the soil.)
Earthwork is one of the major elements of industrial hydroengineering, transportation, and civil engineering construction. The purposes of earthwork are the creation of engineering works from the soil (such as dams, railroads, highways, canals, channels, and trenches), the laying of foundations for buildings and structures which are erected from other materials, the leveling of areas under development for building, and the removal of masses of earth in order to open up mineral deposits (burden removal). Open-pit mining and underground mining work involve earthwork. Works are created from earth by excavating the ground or by raising embankments from the ground (soil). An excavation dug solely for the extraction of soil is called a reserve, and an embankment formed during the pouring off of unnecessary soil is called a dump (dirt pile).
Earthworks may be of the open-cut or open-pit type (on the surface of the ground), underground, or underwater. In modern construction, earthwork is almost completely mechanized and is performed by highly efficient machines. Preliminary and auxiliary tasks include cleaning up of areas, laying out of earthworks, drainage or diversion of surface waters, establishment of drainage systems, strengthening (shoring) of excavation walls, and soil stabilization. Earth-work is done mainly by mechanical, blasting, and hydromechanical methods.
With mechanical excavation methods, which are the most widely used, soil is removed by excavating machines and combination excavating-transporting machines (including excavators, scrapers, bulldozers, graders, grader-elevators, loaders, and trench diggers). For transporting soil (from excavations to dumping locations) over considerable distances, the so-called transport method is used, in which the ground is removed by excavating machines (mainly excavators) and soil is loaded for transport by rail, road, or belt conveyors.
During the construction of canals, channels, railroads, highways, foundation pits, and trenches in which the soil is moved over short distances (150-200 m), a nontransport method is usually used; the excavation of the soil (with few transfers) and its removal beyond the construction contours are done by dragline excavators. This method is extremely efficient, particularly in open-pit mining. The use of self-propelled (power-driven) scrapers and loaders is efficient if the soil must be transported to dump areas over distances up to 3,000 m. Trailer scrapers with 10-15 cu m scoop capacities, which are towed by low-speed tractors, are generally used for moving soil over distances of up to 100 m. By stripping the soil in layers, scrapers make it possible to select high-quality soils for piling in separate dumping grounds. In addition, scrapers smooth out and partly compact the soil, which substantially facilitates subsequent soil stabilization work. Preliminary loosening of hard ground is recommended for scraper work.
Bulldozers are used for shallow earthwork, planing, combined excavation-banking work (on slopes), leveling, and backfilling work with movement of the soil over distances of 100-150 m. The use of groups of bulldozers (two or three in a row) enhances efficiency by increasing the capacity of each bulldozer because of reduced soil loss. Mechanical shovels and multibucket trenching machines are used for digging trenches. Planing work, profiling of earthen roadbeds, and the digging of small trenches (such as catch drains and drainage ditches) may be performed with power-driven graders. Layered soil compaction is required for the erection of various types of earthworks and for the backfilling of foundations, footings, and trenches. This is usually done with road rollers (including drum rollers, spiked rollers, and vibrating rollers) and, in restricted conditions, with tampers, vibrotampers, and tamping plates.
In earthwork employing the blasting method, the explosive charges are placed so as to move the soil in the necessary direction. In many cases (especially in large volume work), the blasting method results in considerable economic savings.
The hydromechanical excavation method, known as hydromechanization, uses hydromonitors (hydraulic excavators), which work the earth mass with the pressure of a water jet, or suction dredges, which suck up the soil together with the water. Under hydromechanization, all three elements of earthwork (excavation, transportation, and piling of the soil) are combined in a continuous operation, which provides the high efficiency of this method. Combination excavation methods, such as the use of the mechanical method in conjunction with the blasting or hydromechanical methods, are also employed. The choice of excavation method and the mechanical equipment depends on the work production plan.
REFERENCESStroitel’nye normy i pravila. Part 3, section B, ch. 1: “Zemlianye sooruzheniia.” Moscow, 1964.
Tekhnologiia i organizatsiia stroitel’nogo proizvodstva. Edited by I. G. Galkin. Moscow, 1969.
L. B. GISIN