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