Earthwork equipment is used for excavation, hard digging, loading, pull or push earth loads, compaction. These are essential equipment in construction field.
These are excavating tools which are more efficient for short haul applications up to 100 m.
For this Dozer a blade his been attached at the machine front side which is a tractor-power unit.
Different Types of Dozers
The classification of different types of Dozers are on the basis of mounting.
The following are the two types based on mounting :
1 . Wheel-Mounted Dozer.
2.Crawler-Mounted dozer.
Wheel – Mounted Dozer
Earthwork equipment-Wheel Dozer
This type of equipment is good soils that have no sharp-edged pieces and firm soils.
This is best used when surface is levelled and to handle downhill earth works.
Compaction and Kneading to ground surface can be done due to its concentrated wheel load.
This equipment is good for works which require long distance travel.
For handling of loose soils this equipment is the best option.
Equipment speeds can be at the range of 8-26 mph and this have fast return speed.
The only drawback with this equipment is, if surface conditions are wet then operation with this equipment can slow down or may stop.
This equipment able to handle only moderate blade loads.
Crawler-Mounted Dozer
Earthwork equipment-Crawler Dozer
This Crawler Dozer can able to work on sharp-edged pieces and on a variety of soils.
This type of equipment can able to work at any terrain.
This can easily able to work over mud slick surfaces and on soft ground.
This equipment is best if the work require short distance travel.
This equipment can handle both loose soils and tight soils.
This equipment speed ranges between 5 to 10 mph and have slow return speeds.
This can able to push moderate and large blade loads .
Calculation of Dozer Output
Dozer output can be calculated using the following formula in vol /hr.
Outout = (Actual operating time in minutes / Time required per trip in minutes ) x ( Rated board capacity in loose volume / Swell factor)
where as, Cycle time or time required per trip in minutes can be calculated using the formula :
Time required = D/R + D/F +G
Where, D = Distance of Haul in n metres, F =Forward speed in m/min , R = Reverse speed in m/min,G= Gear shifting time in min (in general 0.15 min to 0.30 min)
2.Tractors
Tractors are mainly used to push or pull loads and also used for as a mount for many types of equipment such as Shovel, dragline, bulldozer, trenchers, hoe.
The following are the two types of tractors.
1.Wheel Tractor
2.Crawler Tarctor
Wheel Tractor
earthwork equipment-wheel tractor
Wheel Tractors are used for shifting of light weight loads and it is easy to operate with its steering wheel.
The coefficient of traction for this type of tractor is about 0.6 and its speed is 3 to 4 times more than the Crawler tractors.
For smaller distances of work this type of tractors are most suitable and the pressure on ground of wheel Tractor us from 1.25 kg/cm2 to 1.5 kg/cm2.
The wheel Tractors operation,maintaince and repair cost is comparitvely less and but tractors can slip over smooth surfaces.
Crawler Tractors
Earthwork equipment-crawler tractor
This Crawler tractors are generally used for shifting heavy loads on rough surfaces.
It consists of track with endless chain of steel rings made of steel plates connected one by one with bushings and pins which helps for easy movement on rough surfaces.
The traction coefficient of this tractors is 0.9 and this coefficient decides the optimum pull of the tractor
The Crawler tractors have stick control which is difficult to control.
This tractors can be used efficiently on muddy or loose soil as it have a ground pressure of 0.85 kg/cm2 to 1.0 kg/cm2.
The operation, maintenance and repair cost for crawler tractors is more and initial cost for buying them is more compared to Wheel Tractors.
This Crawler tractors can damage concrete and tar pavement when they pass on them.
3.Power Shovel
This Power Shovels are mainly used for loading units and for hard earth digging above track level.
This earthwork equipment can able to excavate all classes of earth but fails in working with solid rocks. If the solid rocks got loosened then this equipment can be used.
The bucket capacity of this Power Shovel is between 0.375 m3 to 5 m3.
Power Shovel Output
The power shovel output can be calculated using the following formula :
Output = (actual time in sec / cycle time in sec) x (Loose volume of dipper / 1+ swell factor ) x efficiency
4.Dragline
The Dragline is a machine which is used for dragging the bucket against the material to be dug.
Its long light boom is more helpful during digging when compared to Power Shovel.
5.Clamshells
This earthwork equipment is used to dig earth in virtical direction.
Most of the characteristics of this Clamshells equipment is similar to Dragline equipment and when the bucket is filled with earth, it works like a crane.
This equipment has bucks hung from a crane and they are like inverted jaws and works with a biting motion.
This Clamshell equipment is more suitable to work at both below and above ground level.
6.Back Hoe / Hoe
BackHoe or Hoe is an earthwork equipment which is used for excavating the soil earth and it comes under PowerShovel group.
This equipment is named as Hoe, as its digging mechanism resembles the ordinary garden hoe, hence the name.
OutPut of Hoe
The output of Hoe can be calculated using the following formula.
Hoe Output = (1/Volume correction ) x (E/60-min.hour) x (3600 sec x QxF/t)
where as,
Q = Full buck capacity, F = Fill factor of bucket for hoe buckets,t = Time cycle in sec, E = Efficiency in minutes per hour.
Volume correction is given by, V = 1/ (1+ swell factor ).
Converting loose soils to tons can be done using the formula : Loose units weight in lb/ 2000 lb per ton.
7.Scraper
The Scraper is an earthwork equipment which is used for scraping the ground , loading it simultaneously, can transport the load and can dump at desired locations.
It can also used for spreading the dumpped earth or materials at required area and at required levels.
Scraper Output
The scraper output can be calculated using the following formula :
Scraper output = S x Optimum loose volume per trip x 60 x efficiency / t
where, t= Time cycle per trip in min, S=Swell factor depending upon the type of soil.
8.Compactors
earthwork equipment-compactor
By applying energy to the soil using pressure, kneading, vibration and impact methods compaction occurs.
The following are the 11 types of compacting equipments.
1.Vibrating compactors
2.Tamping rollers
3.Sheepsfoot roller
4.Padded drum vibratory soil compactors
5.Towed Impact compactors
6.Smooth drum vibratory soil compactors
7.Compaction wheels
8.Manually operated Vibratory plate compactors
9.Pneumatic tired rollers
10.Manually operated rammer compactors
11.Pneumatic tired rollers with variable inflation pressure
1.Vibrating compactors
The vibration effect can be measured using frequency and amplitude.
In vibrating compactors, the depth or effective area of vibration to be transmitted into soil in controlled by amplitude.
2.Tamping rollers
Tamping rollers are non-vibratory rollers,they have high speed and are self-propelled.
This earthwork equipment rollers are most suitable in all soils except sand.
3.Sheepsfoot roller
This type of rollers are more effective for fine-grained soils compaction.
The only drawback with this earthwork equipment equipment is, that it cannot be used on granular materials which are cohesionless.
4.Paded drum Vibratory soil compactors
For soils having Plasticity index (PI) 5 or more with 50% of materials ,this equipment is more suitable.
This earthwork equipment are used mostly for working in confined areas or the trench works.
5.Towed impact compactors
This Towed compactors are used for giving sharp blows in sand, silt, rock, gravel and clay.
This earthwork compactors consists of 3 to 5 drums which rotates during movement and again lifts and falls back to the ground by itself.
6.Smooth drum vibratory soil compactors
This compactors are more suitable with particle sizes ranging from fine sand to large rocks and for soil with 10% of materials and having Plasticity index (PI) 5 or more.
These compactors uses pressure,vibration and impact forces for compacting the soils.
7.Compaction wheels
For achieving compaction while soil back filling in utility trenches ,compaction wheels are attached to excavator boom to avoid hazards to the working men in trenches.
8.Manually operated vibratory plate compactors
For consolidating soils where large earthwork equipments are not practically possible, this self propelled plate compactors are used.
9. Pneumatic tired rollers
This earthwork equipment rollers perform compaction of soil below surface by using kneading method.
These earthwork equipment is more effective for rolling in earth fill dams,airfield bases and roadway subgrades.
10.Manually operated rammer compactors
The usage of this earthwork equipment rammer compactors are effective in Soil areas where moisture content is controlled carefully and having less lifting thickness, generally 3 to 4 inches.
11.Pneumatic tired rollers with vibrable inflation pressures
This earthwork equipment rollers use tires for compacting the soil by applying pressure.
Low tire pressure is applied when equipment passes first time on soils,gradually pressure increases and soil is compacted to meet the particular conditions of the soil.
Output of roller compactors
The roller compactor earthwork equipment output can be calculated using the formula :
Output = L x S x W x efficiency x 16.3/n
Where, W = compacted width per roller pass, S = roller speed average in miles per hour, L=compacted list thickness in inches, n = To achieve required density number of roller passes required.
Equipment engineering fundamentals
The following are the important fundamentals of equipments.
1.Grade resistance
2.Drawbar pull
3.Rolling resistance
4.Rimpull
5. Temperature and pressure effect on IC engine
6.Cost of Depreciation
1. Grade resistance
This grade resistance is the physical property which depends on type of construction, type of road and type of equipment.
For each 1% of grade, the required tractive effort for every 10 kg per gross ton of weight may increase if slope increases and decrease if slope decreases.
2.Drawbar pull
Effective drawbar pull can be calculated using the following formula :
Drawbar pull = Rolling resistance +grade resistance +drawbar pull available.
3.Rolling resistance
The rolling resistance of an equipment can be calculated by:
Rolling resistance R = P/W
Where, W = Gross weight of equipment in tons, P = Required tractive force in Kgs.
The average tension in the cable can be measured by placing dynamometer in the low cable.
4. Rimpull
The rimpull defines the force of traction between the surface on which the tires operate and the driving wheels rubber tires and expressed in kgs.
Maximum RimPull can be calculated If the traction coefficient is high such that slippage can be eliminated using the formula
Rimpull = HP x 375 x Efficiency / speed in mph.
Maximum rimpull can be calculated if the traction coefficient is that before the rated capacity if slippage starts using the following formula :
RimPull = Total pressure between the surface and the driving wheels x traction coefficient.
5.Temeprature and pressure effect on IC engine
Under standard conditions of pressure and temperature the rated horsepower of an IC engine is tested.
Under different conditions if the test is done,then the horsepower of engine can be calculated using the formula :
Corrected horsepower Hc= Ps/Po x Ho x root of To/Ts.
Where ,Ho = Horsepower observed determined from test, Hc = Corrected horsepower,
Po= Barometric pressure observed in mm, Ps= Standard barometric pressure,Ts= Absolute temperature for standard conditions, To = Absolute observed temperature.
6.Cost of depreciation
Cost of investment :
Annual investment cost of equipment = 10 to 20% of the average annual cost of the equipment.
The average annual cost can be calculated using the following methods.
Case I: IF the salvage value of equipment is zero
Average annual cost Pav = P (n+1)/2n
Where, P= Total initial Cost, n = life period in years.
Case II: If salvage value of the equipment is not zero
Average annul cost Pav = (P(n+1) + s(n-1))/2n
Where, P= Total original cost, n= life period in years ,s = Salvage value.
Fuel consumption cost
For a gasoline engine, the consumption fuel of can be calculated using the formula :
Fuel Consumption Ltr /hr = rated HP x operating factor x 0.3
For Diesel engine, Fuel consumption can be calculated by :
Fuel consumption in Ltr /hr= rated HP x operating factor x 0.2
The operating factor is given by = time factor x engine factor
Lubricating Oil cost
Quantity of consumed lubricating oil can be calculated using the following formula :
Quantity consumed(q) in ltr /hr = (Operating factor x 0.003 Kg per HP-hr x rated HP / 0.74 kg per liter)+ C/t.
Where,C = Crank case capacity of engine in liter, t = number of hour changes and the operating factor can be assumed 0.6 if sufficient data is not available.
Annual depreciation
Annual depreciation can be calculated using the following formula :
Depreciation = (Initial value – Salvage value )/Used equipment period in years.
Initial value of equipment = price of equipment + loading and unloading charges + transport charges +Installation charges.
Conclusion :
The above mentioned 8 earthwork equipments are essential and used in the construction field and the above-mentioned fundamentals of equipment should be considered while dealing with this earthwork equipment.
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