mechanized equipment for a variety of jobs in building, maintaining, and repairing roads and railroads, as well as in hydraulic engineering, airport construction, and industrial and public projects. Modern roading machines include both independent machines and units made for mounting on or hitching to wheeled or caterpillar-tread tractors.
Modern road-building and maintenance machinery can be classified by the type of work performed. There are machines that do the preparatory work (tree-dozers, brushcutters, stumpers, scarifiers, turf-cutters), machines that do the earthwork (excavators, scrapers, bulldozers, power graders, road harrows, dirt trucks), machines that lay down gravel, rock, and stabilizing covers (machines that spread rock and binding materials and that compact asphalt and concrete), machines that build asphalt-concrete roads (mixers and asphalt-concrete spreaders), machines that lay cement and concrete paving (rail forms and equipment for installing them, countouring machinery, machines that spread concrete and cut expansion joints, concrete-finishing machines, and machines that spread film-forming liquids), and machines that maintain and repair roads (sand spreaders, road sweepers, sprinklers, snowplows, repair trucks). Roading machines perform both the basic work (earthwork, improvement of light-duty and intermediate road surfaces, construction of asphalt-concrete roads, laying of concrete-cement paving) and auxiliary (preparatory) work. They are also used in maintaining and repairing roads.
Both general-purpose earth-handling equipment (excavators, scrapers, bulldozers, graders, power graders, elevating graders) and special road harrows are used for the earthwork in road building and repair. Road rollers and tampers are used to compact the earth. When dirt brought in by dump trucks, scrapers, and other equipment is put down in layers, it is compacted by self-powered and trailer-mounted sheeps-foot and pneumatic-tired road rollers, vibrators, and tampers (impact type and vibrator type).
In the construction of bases and the improved light-duty and intermediate road surfacings, roading machines spread crushed rock, gravel, and grit and haul binding materials (when laying surfaces of mixed materials). A crushed-rock and gravel spreader lays down crushed rock in a layer up to 250 mm thick and 3,100 to 3,600 mm wide. This machine has an attachment that makes a crossfall of the road surfaces and two vibrator plates that compact the crushed rock. This kind of spreader can lay down as much as 100 tons per hour. The spreader for small rock is mounted on a dumptruck. Small rock moves from the body of the truck into a spreader and through a control gate to be spread on the roadbed. The machine can cover as much as 800 sq m per hour. Road oilers and bitumen trucks are used to spread binding materials. These machines are either semitrailers or mounted on self-powered chassis. In building bases, machines are used that pulverize and strengthen (stabilize) local or hauled earth gravel, and crushed rock by mixing them with organic binding materials (tar, bitumen, emulsion) or inorganic binding materials (cement, lime). For small projects, trailer-drawn or mounted road harrows (mounted on tractors, power graders, and special twin-axle wheeled chassis) and cement spreaders are used; single-pass mixers are used for large projects. Gravel and crushed rock are also mixed with binding materials in a three-in-one assembly consisting of a caterpillar-tread chain-bucket loading shovel, which is at the same time a tractor, a mobile mixer, and a spreader. Asphalt-concrete mixers and asphalt-concrete spreaders are used in preparing, laying, uniformly spreading, and compacting asphalt-concrete surfaces. Bitumen trucks transport, store, stir, and apply the bituminous mixture for asphalt-concrete surfaces.
For cement-concrete surfaces, a complex of machinery is used to prepare the base, set up the rail forms, spread the concrete on the base, compact it, finish the surface, provide expansion joints and smooth them off, and work the freshly poured concrete. This complex of machinery includes equipment that sets up the rail forms and tractor-mounted equipment that grades the underlying layer of sand and compacts it and connects and fastens the units of the rail forms. A self-powered rail layer is used for this purpose, as well as a base profiler, which moves along the rail forms, shapes the layer of sand with a special blade, and compacts the sand with a vibrator beam by passing over it once or twice to a depth of 300 mm over a section 3.5-7 m wide. The cement-concrete mix is spread in an even layer over the entire width of the base by concrete spreaders that operate either continuously or periodically. Concrete finishing machines level, compact, and smooth the cement-concrete mixture. Concrete spreaders are classified according to principle of operation as tampers or vibrators and as wheeled, rail-mounted, or caterpillar according to manner of locomotion. The working parts of concrete-finishing machines, which float the surface, are.a leveling beam, a tamping beam, and a smoothing band or plate. Special smoothing machines, which are up to 7 m wide and can handle between 40 and 80 cu m per hour, are also used. In addition, there are concrete layers that can handle all three stages: cement pouring, leveling, and compacting.
Cutters cut expansion joints, with vibrating cutting devices in freshly poured concrete and with abrasive disks in concrete that has set (eight to 12 hours after pouring). Cross-joints are cut with a vibrating knife, and longitudinal joints are cut with a vibrating disk. In order to make the concrete near the joint smooth and to prevent it from warping, a plate is mounted on the machine in such a way that the disk passes through it. At the back of the machine there is a device to fill the joints with a special mastic. A machine that spreads film--forming fluid in order to form a moistureproof film on the surface of the freshly poured concrete and to prevent it from cracking has a sectional frame on a power-driven chassis and a carriage that moves along it. Nozzles on the carriage spray an emulsion and lime solution under pressure. A compressor and tanks for the emulsion are on the frame, taking in an area 3.5 to 7 m wide at a rate of 1,500 to 3,000 cu m per hour.
Machines for preparatory work clear the way of timber, brush, roots, and turf and loosen up hard or rocky ground. This group of machines, with equipment mounted on or hitched to tractors, includes tree-dozers and brushcutters with wedge-shaped blades and base-mounted knives, in front of which are wedge-shaped blades for splitting stumps and moving trees out of the way, stump loaders with blades and special teeth, turf-cutters, which cut turf up to 30 cm in width, and scarifiers, on the frames of which are mounted powerful teeth to break up hard ground to depths up to 70 cm and to break up gravel and crushed rock or asphalt-concrete surfaces.
Machines that maintain and repair roads are municipal machinery. Sweepers and cleaning machines pick up trash from the roadway by means of rotating cylindrical and conical brushes and feed the trash to a conveyor, from which it is dumped into a hopper. Cleaning work is done by sprinkling, pneumatically or in other ways. In addition to self-powered equipment, trailer-mounted brushes with sprinkling devices are used. Sprinkling and watering machines are used not only on road surfaces but also to irrigate roadside greenery and to put out fires. As a rule, these machines are mounted on truck chassis and have tanks that hold up to 6,000 liters, as well as centrifugal pumps and sprayers to distribute the water. Snow is cleared from roads with plow-type and rotary snow removers. The working element of the plow-type snow removers, the plow, is mounted in front of a truck or tractor. As a rule, rotary snow removers have two working parts, one of which (a screw, blade, or plow) cuts the snow and delivers it to the second, a rotor that throws the snow as much as 20 m away. Rotary-screw snow removers are widely used. They can be mounted on trucks, tractors, or wheeled power units. Snow is loaded into haulers by a snow loader, whose working part is a disk and feeder device with claws that gather in the snow and send it to a cleated conveyor belt, which delivers it to the hauling unit. A snow loader is mounted on a truck. Sand spreaders spread sand on roads (to increase traction on the surface of the road when icy): a cleated conveyor belt delivers sand from the metal body of the truck to a funnel, from which it falls onto a spinning disk which distributes it (a rotary-table feeder). The following are used for repair work: devices that warm and soften the asphalt surfaces when removing or leveling it, asphalt spreaders, bitumen pourers for filling in cracks in asphalt surfaces, and concrete breakers to break up cement-concrete surfaces and bases in repairing roads and laying cables and sewerage. All these machines are mounted on trucks and have specialized equipment. Road repair and maintenance uses tractor- or miniature wheeled-tractor-mounted equipment: mowers to cut grass on shoulders, slopes, and ditches; drills for drilling holes; post-hole diggers for drilling holes and placing pillars, road signs, and posts; brooms to sweep roads; ditchers; scoop loaders, fork lifts; and machines for clearing ditches of sediment and reshaping the earth around them. Power graders or, less often, ordinary graders, bulldozers, and other earthmoving equipment are also used to repair dirt and gravel roads.
Modern trends in the design of reading machinery aim at increasing productivity, dependability, service life, and maneuverability; reducing the cost and the amount of metal and power consumed; automating operations more extensively; creating chassis for many types of equipment and using various types of truck-mounted equipment; developing multipurpose equipment; unifying and standardizing units and parts, and making use of new materials.
REFERENCESDorozhno-stroitel’nye mashiny: Spravochnoe posobie, 3rd ed. Moscow, 1963.
Balovnev, V. I., I. A. Zasov, and Iu. L. Karaban. Mashiny dlia soderzhaniia i remonta avtomobilnykh dorog i aerodromov. Moscow, 1964.
Spravochnik konstruktora dorozhnykh mashin. Edited by I. P. Borodachev. Moscow, 1965.
Dorozhno-stroitel’nye mashiny. Moscow, 1965.
Polosin-Nikitin, S. M. Mekhanizatsiia dorozhnykh rabot. Moscow, 1966.
Dorozhnye mashiny. Leningrad, 1968.
E. A. KAMENSKAIA and S. A. SOLOMONOV