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Construction equipmentsConstruction equipments are broadly classified inthe following category;
Earth moving Equipments.
Hoisting equipments.
Concreting equipments.
Stone crushing equipments
Specialised equipments used in bridges, tunnels etc..
Earth moving equipmentsEarth moving equipments include;
Dozers
Scrapers
Excavators like shovel & hoe
Dragline & Clamshell
Soil compacting equipments
Hauling equipments.
DozersDozing means pushing material
Bull doze means push in forward direction with blade perpendicular to the direction of motion of equipment.
Angle doze means pushing in forward and towards one side with blade at an inclination to the direction of movement of equipment.
Dozers are self propelled equipments which are either track mounted or wheel mounted.
Track mounted dozers are having less speed but can move on any type of terrain while wheel mounted dozers have more speed and need at least rough road to move.
IS 4988 part 2 lays the standards for Bull dozers
Schematic diagram of a Bull dozer
Functions of Dozers Shallow excavations up to 300 mm deep on
either level ground or side hill cutting. Moving earth or rock for short haul distances up
to about 90 m. Spreading earth or rock-fill, or backfilling
trenches. Opening up pilot roads through mountains or
rocky terrain. Clearing land of shrub and small trees. Acting as towing or pushing prime mover for
scraper.
Bull dozer in site with extended blade
Angle dozer
Cycle time for dozerThe cycle of operation for dozers can be divided in to three parts ;
Pushing (Actual pushing of material).
Returning (Returning after haul).
Maneuvering ( Turning & Positioning for fresh push).
Accordingly cycle time is divided in to ;
Pushing time ( Approximately the total cycle time).
Returning time ( Approximately 60% of pushing time).
Maneuvering time(10% of pushing time).
Sample calculation of output of Dozer
Note : lcy= loose cubic yard. If we consider ideal working as 50min/hour, then production = [50/60] 424 lcy/hr = 353.33 lcySimilarly if 25% swelling is considered, production = [353.33/1.25] = 282.66 bcy (bank cubic yards)
SCRAPERScrapers are earth moving equipments designed to load, haul and dump loose material.
Scrapers are pulled by tractors or self propelled.
The haul distance of scarper is in the range of 120m to 1200 m.
IS 4988 part 3 & IS 10856 standardise scraper
Schematic diagram of scraper
Main parts of ScraperBowl : Load carrying component of scraper.Apron : Front wall of bowl with raising & lowering mechanism.Ejector : Movable rear wall of bowl which moves forward whileunloading.Scraper operations : Loading loose material.Hauling over medium distances.Spreading loose material at the dump site.Cycle of operations with cycle time:o Traveling over the haul distance with load and returning emptywith cycle time about 80% of the total cycle time.oLoading with cycle time 15% that of travel timeoDumping with cycle time about 8% of travel time.oManeuvering with cycle time about 8% of travel time
Scraper at site
Earth excavatorsExcavators are equipments which excavate earth,lift the excavated earth and load a hauling unit.
Front shovel & Back hoe are two versatileexcavators.
Front shovel:
Front shovel is a track mounted excavatorpredominantly used for hard digging above thelevel of equipment base.
The travel speed is less than 10 km/hr.
Angle of swing is 3600
Bucket capacity varies from 3 to 10 cubic yards.
Schematic diagram of hydraulic front shovel
Typical hydraulic front shovel
Shovel operationsFront shovel excavate any type of soilexcept un fractured hard rock.
Cycle of operations :
Cutting the earth.
Swinging in loaded condition.
Unloading.
Swinging back in empty condition.
Maneuvering to proceed for fresh cut.
Factors affecting production :
Type of material.
Angle of swing.
Typical calculation for output of a shovel
Back hoeBack hoe is an excavator used to excavate below the natural surface of ground on which the equipment rests.
Back hoe is track or wheel mounted.
Operations :
Back hoe is best suited for excavation of trenches.
Back hoe can also be used for loading excavated material.
Operation cycle:
Loading Bucket
Swinging load
Dumping load
Empty swing
Schematic view of Back hoe
Back hoe excavating trench
Back hoe used as loader for loose material
Production capacity of hoe depends on:
The size of bucket
Depth of digging
Height of loading
Type of material
DraglineDragline consists of bucket attachment hanging from a crawlermounted lattice crane. It excavates soft to medium hard soils andloose materials.Loading of dragline is done by dragging the bucket towards themachine.Bucket capacity of dragline is smaller than shovel & Back hoe. Theadvantage of dragline is its long reach for digging & Dumping.Operations :Excavating soft & medium hard soils, loose materials, removal ofweeds from ponds and reservoirs.Dragline production depends on ;Type of materialDepth of cutAngle of swingLength of boom
Schematic diagram of dragline
Efficient zones for dragline digging
ClamshellClamshell consists of bucket comprising of twoscoops hinged together.
Clamshell is a vertically operated attachment &can work above & below groundlevel.
Clamshell is efficient in handling loose materialslike sand, gravel, coal, wet material etc..
Typical clamshell bucket
Clamshell loading & un loading
Soil compacting equipmentsModes of soil compaction: Static compaction : The static load overcomes the
internal friction between soil particles readjusting them to denser position.
Impact compaction : The load is very high due to impulse characteristic. The shock of impact overcomes the internal friction between soil particles resulting in readjustment of particles to denser position.
Vibratory compaction : Vibration reduces the internal friction between soil particles resulting in readjustment of particles to denser position.
Kneading compaction : Kneading action results in very high localised stresses which overcome internal friction between soil particles readjusting them in to denser position.
Modes of compaction
Types of soil compacting equipments
Smooth wheel roller ( Static Mode ofcompaction)
Pneumatic wheel roller ( Static Mode ofcompaction)
Smooth wheel vibratory roller (Vibrating modeof compaction)
Sheep foot roller ( Kneading compaction)
Vibratory plate compactor (Vibrating mode ofcompaction)
Smooth wheel roller
Pneumatic wheel roller
Smooth Wheel vibratory roller
Single wheel vibratory roller
Tandem wheel vibratory roller
Sheep foot roller
Two drum towed type sheep foot roller
Vibrating plate compactor
Selecting type of compacting equipment
Vib.= Vibratory, SWSR = Smooth wheel steel roller, PTR = Pneumatic tired roller
Hauling equipmentsHauling vehicles are used to haul earth and othermaterials in the construction site.They include trucks, dumpers and trailers.Hauling vehicles are classified as; On the road vehicles which are licensed tooperate on highway and axle loads, length, width &height with in limits permitted under the rulesprescribed by Central Motor Vehicle Rules (CMVR).[ 10.2 M.T( single axle) 19 M.T. (Tandem axle) ,
16m, 2.7 m & 4.2 m respectively]Off highway vehicles which are not licensed forhighway operation and have higher axle loads anddimensions permitted on highway. These haulingvehicles are operated within project sites.
Pay load of haulage vehicleIt is the revenue earning capacity of haulage vehicle.
Pay load is either gravimetric or Volumetric.
Volumetric pay load may be struck volume or heap volume.
Dump truck with tipping arrangement
On highway bottom dump truck
Off highway bottom dump trailer towed by tractor