Category: Earth Works

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Earth Works Road Construction

Loader Operator Techniques used in Pit

In  any  pit-type  operation  the  loader  is  the  key  (major  role)  machine  in  determine  the  rate  of production.  To  ensure  that  this  machine  is  worked  continuously  and  efficiently  the  following points should be observed :

(1)     Although  most  loaders  are  extremely  manoeuvrable  and  can  load  under  awkward conditions,  the  best  production  is  obtained  if  the  angle  of  turn  and  walking  distance  is
kept to a minimum.

(2)     Ensure the loader operator keeps the floor of the excavation clean and level.

(3)     Provide  a  near  vertical  face  on  a  stockpile  to  assist  loading  efficiency.  If  possible  the operator should have his back to the wind.

(4)     Most loader-digging is done with the bucket flat or tilted to a slight downward angle. This position gives maximum penetration into banks and high spots, and cuts a smooth path for the loader’s tracks or wheels. The flat position is bets for pushing up a quantity of loose material, but the bucket should be turned down steeply for spreading and grading so that the material will flow freely from the bucket.

(5)    For normal soils, the method is to force the bucket into the toe of the bank and then lift. It is often desirable to crowd the filled bucket against the upper part of the bank to break up the material so that it will slide down to the where it can be picked up easily on the next pass.

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Earth Works Road Construction

Earthworks – Loading and Hauling Material

Equipment Most Commonly Used

Where haul distances render dozer operation uneconomical, material is moved either by loading into trucks or by means of scrapers.

A  variety  of  trucks  is  available  for  hauling  loose  materials  on  earthworks  jobs  as  well  as  the conventional  highway truck, there are off-highway  vehicles which  have  fewer axles than their highway counterpart and whose axle loads exceed the regulation limits.

(a)  Highway Trucks  with  general  purpose  tipping  bodies  are  suitable  for  the  cartage  of materials  from  outside  sources  to the  site  of  work,  and  for  the  cartage  and  distribution  of material on the site.

They can operate at comparatively high speeds on the site but require a reasonably firm and smooth ground surface. As they bog easily they are unsuitable on soft sites.

Their  main  application  is  for  very  long  hauls  where  haul  roads  are  good  and  axle  load limitations apply (e.g. for hauling selected fill from a pit outside the limits of the works).

(b) Off-Highway Trucks  are suitable for hauls of up to 3 km at relatively high speed on good haul  roads  but  at reduced  speed  when  working  on  soft  ground. They  are  usually  the  most suitable equipment for hauling shot rock (unless the lead is very short in which case a dozer might be used).

Their axle loads are usually high and, unless they are equipped with abnormally large tyres they may bog on wet sites. Also, one large vehicle may do more damage to a haul road than several small ones.

Their  larger  body  offer  a  bigger  loading  target  for  the  loader  bucket  which  may  increase production of the loader. The high sided body of some of the larger wagons may however, be unsuitable  for  some  types  of  loaders.  (This  possibility  should  always  be  investigated  when matching loaders and trucks).

Owing  to  their  large  capacity  they  are  more  economical  than  smaller  machines  under conditions where they can develop their speed and where they are not delayed by restrictions at the loading and tipping points, but the breakdown of a large carrying unit causes a greater proportional loss of output than that of a smaller unit.

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Earth Works Road Construction

Terms Used in Earthworks – Part2

Previous part of the terms used in earthworks can be accessed here. These typical terms are used in earthworks in regularly.

Cutting : That portion of the road where the finished road surface is below natural surface.
(cut)

Earthworks : All operations involved in loosening, removing and depositing or compacting earth, soil, or rock; or the material when so placed.

Embankment * : A bank or fill.

Fill : • The depth from the finished road surface to the natural surface below.
• That portion of a road where the  pavement surface  is above the natural surface.

Grade : • To design the longitudinal profile of a road.
• To secure a predetermined level of inclination to a road or other surface.
• To shape or smooth an earth, gravel, or other surface by means of a motor grader or similar implement.

• To arrange aggregate or other material in accordance with particle sizes.

Grading : The percentage of the various grain sizes present in a soil or other material.

Grading : The operation of shaping the surface of a road to a definite longitudinal and cross section , either mechanically or by hand.

Grubbing *: The removal from the ground of trees, roots, stumps, small rocks etc. to a depth of one foot below the surface of the ground.

Haul : The distance through which material is transported between points of leading and unloading.
(Lead)

Pit : An open surface working from which sand, gravel, or earth is excavated from its natural bed.

Selected filling : Filling in accordance with requirements set out.

Settlement : A downward movement of the soil or of the structure it supports by the reduction of the voids in the underlying ground.

Side cut : That portion of a road on sloping ground where one edge only of the formation is in cut and the other edge is on the natural surface or on fill.

Sidelong (ground) : Sloping transversely to the road.

Spoil : Surplus excavated material.

Stockpile : A heap or stack of material held in stock for future use.

 Stripping  : The removal of the upper layer or soil or over burden (including contained roots, humus or stones); or the material so removed.

Sub-grade : The trimmed or prepared portion of the formation on which the  pavement  is constructed.

Surface formation : The excavation, removal and proper utilization in low  embankment construction  of material from the route of the road or from borrow pits, usually adjacent to the road.

Tamping : • The compaction of a loose material or a surfacing by repeated blows.
• The placing and packing of filling material in a drill hole, either above the explosive charges or between and above the  explosive charges .

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Earth Works Road Construction

Terms Used in Earthworks – Part 1

The following terms used in earthworks regularly. You need to understand these terms thoroughly will help you to read and communicate with others very well.  

Backfilling     :  The material replaced in an excavation.

Batter              :The uniform side slope of walls, banks, cuttings etc.The  degree of such slope, usually expressed as – horizontal to 1 vertical as distinct from grade.

Batter             :  To from a uniform side slope to a wall, bank, or cutting.

Bench             : A ledge cut in the batter of a cutting in a curve to provide sight distance. A ledge cut or formed in the batter of a cutting or bank to provide greater security against slips.

 Borrow           :  Filling obtained by excavating at some point other than the cuttings required for the construction of the road.

Borrow          :  To obtain  filling  from some point other than the excavation required for the work.

Borrow pit   :  An excavation outside the formation limits for obtaining filling.

Box cut          :  That portion of the road where both sides are in cut.

Boxing            :  The space formed above the level of the sub-grade by the shoulders to receive the paving material.(Box)

Clearing   *    :  Felling of all trees and scrub – by cutting or breaking off not higher than 0.7 m above ground level including the removal of all artificial obstructions including fences,old buildings, unless otherwise specified.  (  Grubbing )

Compaction  :  The process of reducing the volume of a material by including the closer packing of its particles by rolling, tamping, or other mechanical means.

Compact       :  To reduce the volume of a material by including the closer packing of its particles by rolling, tamping or other mechanical means.

Consolidation :  The process by which earth or soil reduces in volume over a period of time usually involving loss of water.

Consolidate  :  To reduce in volume naturally.

Cut                   :  The depth from natural surface of the ground to the finished road surface below.

Next part of the terms in  earthwork construction  can be accessed here. These typical terms are used in construction works in regularly

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Earth Works Road Construction

Methods of Loosening Materials

Methods of loosening materials either by scarifying , ripping or drilling and blasting. Scarifying will be suitable only for loosening thin layers of soil, usually in conjunction with a grading  operation . Rippers may be used to loosen soil., decomposed rock and even hard rock provided it is sufficiently jointed and fissured to enable it to be ripped to the required size for the hauling  plant  and be handled by the hauling  plant  and where it is to be used in  embankments , to meet the size limitations placed on the embankment material by the specification.

Where reasonable production rates can be maintained, ripping is cheaper than blasting.

Methods of loosening materials should be carried out with the minimum disturbance to batters and the sub grade. Where ripping is producing unstable batters, blasting may have to be used to remove the material adjacent to the batter.

Preliminary seismic reports will give some indication of the material rippability and the depth at which the various layers are likely to be encountered. Where doubt exists, monitoring of ripping costs should be undertaken. In particular the quantity of material ripped per hour will indicate when blasting should be considered.

If it becomes obvious that ripping is not economical, or that excessive strain is being placed on the ripper and tractor the rock must be blasted. Continued ripping can in fact make future drilling and blasting more difficult.

Ripping should be discontinued when fragmentation of the rock strata produces rock sizes larger than the specification limits. When this is the case properly designed blasting should produce suitable material for specification requirements.

Where both ripping and blasting is required on the job,  works  can be planned with sufficient flexibility for ripping teams and blasting teams to be used at appropriate times, in different locations.

It must be appreciated that a change from ripping to drilling and blasting takes time and incurs non-productive costs and delays. By implementing a large scale blasting operation cots can be reduced to be comparable with difficult ripping. Consequently on jobs where most of the rock required blasting isolated areas that may be capable of ripping might well be shot at minimal extra direct cost, offsetting otherwise additional unproductive cots involved in obtaining a ripping unit. Also, better fragmentation is normally obtained if the soil rock is overlain with a collar of rippable work. First part of the  earthmoving operations  can be accessed here.

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Earth Works Road Construction

Earth Moving Operations

The main  earth moving  operations associated with road construction are :-

(1)     Stripping vegetation and topsoil

(2)     Loosening material in cuttings and borrow pits

(3)     Excavating material

(4)     Loading material and hauling to the embankment (or to spoil)

(5)     Spreading, shaping, watering, compacting and trimming the fill material.

STRIPPING VEGETATION AND TOP SOIL

Prior  to   excavating  material   for  use  in   embankments ,  all  surface  vegetation  must  be  stripped from the area to be excavated. This material is unsuitable for embankment  construction  but may be required together with the top soil for revegetating batters or for forming catch banks. Where batters are to be revegetated sufficient top soil (usually 50-100  mm)  must also be removed to cover  the  batters  to  the  required  depth.

Also  the  whole  surface  on  which  embankments  are  to  be  constructed  must  be  stripped  of  all grasses  and  other  vegetable  matter.  This  striping  operation  is  usually  best  carried  out  with  a dozer.

Any stripped material required for revegetation of batter or catch banks must be stockpiled in a location where it will readily be accessible when required during the construction of cutting and embankments but not in such a locations that it will obstruct the earth moving  operations .

 

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Earth Works Road Construction

Controlling Earthmoving Plant

In order to ensure that controlling earthmoving plant is used in the most economical manner the supervisor must :-

•    Work with the civil engineer to estimate the anticipated (target) out put per hour (or day or week) for each machine and earthmoving plant hours required to complete each major task.

•    Work with the quantity surveyor to estimate, from plant hire and wages etc., the cost of completion the earthwork in the programmed time using the earthmoving plant selected. Check to ensure the work can be performed within the amount provided in the estimate.

•    Study each operation carefully as it begins and check cycle times etc. to see if improvements can be made.

•    During the progress of the work, check that target outputs are being achieved by earthmoving plant.

•    Always think ahead and anticipate problems. What happens for example, if motor grader or roller breaks down ? Have an alternative plan ready.

•    Controlling earthmoving plant that Ensure plant fleet is balanced, i.e. machine capacities are matched as far as possible, e.g. loader output matches trucking capacity.

•    Always make the best use of the driver instructor.

•    Ensure that operators are properly directed by the earthmoving plant supervisor.

•    Watch  plant  operations  closely  for  faulty  techniques  and  have  these  corrected.  (Poor operating techniques can reduce output by 50%).

•    Use human relations skills to get the best out of the  earthmoving plant  operators. They are key men on the job.

•    Ensure  machines  are  not  abused.  If  a  machine  has  to  be  continually  pushed  beyond  its capacity, look for a better way of doing the job or get a better machine.

•    Check that the servicing of plant is being carried out. Discuss any problems with the  earthmoving plant  inspector.

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Earth Works Road Construction

Earthmoving Plant operations

The earthmoving plant carrying out  earthworks operations  should be well balanced and compatible. The various machines should be of machined capacity and power rating and so machine should work below capacity. A perfect solution is rare and perhaps not entirely desirable as a slight excess of compaction and loading capacity is always useful- compaction  because quality control of the fill is so critical and loading because if forces the pace, with any spare time being usefully employed in clearing the loading are and surrounding areas.

The selection of earthmoving plant may be simplified by deciding the ‘major role’ plant item first and then matching auxiliary (secondary role) plant to it. The ‘major role’ plant item is the one required to handle major  earthworks activity . In most roadway excavation the key ‘major role’ item is usually the scraper or the loading unit.

Once the major role item has been selected from available  earthmoving plant , and its movements decided, auxiliary (secondary role) plant to it. The ‘major role’ plant item is the one required to handle major  earthworks activity . In most  roadwork excavation  the key ‘major role’ item is usually the scraper or the loading unit.

Once the major role item has been selected from available earthmoving plant, and its movements decided, auxiliary units can more easily be selected as the quantity of material to be handled and major role plant cycle times are known. For example, pusher requirements must be matched to the scraper cycle time; truck turnaround time must be matched to the loader cycle time and the rate of compaction must match the rate of delivery.

Of course, the above presupposes that the supporting units are of appropriate size and effectiveness, e.g.

• the pusher should preferably have greater power than the scrapper.
• the loader should fill a dump truck in a minimum number of uniform bucket loads.
• the roller(s) should suit the thickness of lift and material.

Because of earthmoving plant breakdowns, changing haulage leads and site conditions etc. continual monitoring and adjustment of operation are required to maintain, as far as possible, the balance of the plant fleet.

Close supervision and direction of operators is essential. Operators must know exactly what they are required to do. Often a short explanation of the reasons for a direction will assist in getting the right result.

Most items of construction or  earthmoving plant  usually require an operator’s full attention. Therefore sites to direct, control and guide operations.

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Earth Works Road Construction

Earthworks Construction Planning

In earthworks construction planning, there are two golden rules, and these must be borne in mind during the planning of the job. They are :-

(1)     Never double handle material, and

(2)     Whenever possible, load and carry material downhill.

The Engineer must plan to ensure that :-

•    The standards set out in the plans and specifications are achieved,

•    The  best  use  is  made  of  the  available  plant.  (He  must  appreciate  the  applicability  and limitation of each type of machine).

•    Whenever possible, available materials are used in the most appropriate position.

•    Work is taken forward on a face with finishing and trimming being carried out as the  work proceeds .

•    Haul roads are carefully located and grades are satisfactory.

•    Cuttings and fills are always properly drained.

•    Culvert laying is sufficiently ahead of  earthworks  so as not to cause delays.

•    Satisfactory provision is made for the  safe  and convenient passage of  traffic .

•    Account is taken of things likely freedom of operations, e.g. allowable loads on bridges and culverts, utility authorities’ services and mains etc.

•    Work on sections likely to bog equipment during the wet is, if possible, carried out during the dry season.

•    Work is carried out in accordance with the earthworks program.

Typical set of rules that apply for  earthworks construction planning  are not limited to above and if you need additional information, see related posts.

 

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Earth Works Road Construction

Pre-construction Planning & Programming of Earthworks

This is last section of pre-construction planning & programming of earthworks constructions  and stick to this procedure will bring-down the unnecessary problems in future.

(k) Material Quantities and Lengths of Haul. It is necessary to determine the quantities of material to be led to embankment, spoiled or borrowed. These quantities and the lengths of hauls must be determined so that appropriate plant can be selected and the work planned. The mass haul diagram is provided in the documents for this purpose.

(l) Selection of Material. The job must be planned so that the various materials available are used wherever possible in the position in the embankment where they will be most advantageous.

(m) Testing and Quality Control. The resource needs must be determined and testers and equipment must be ready so that testing can commence as soon as the earthworks begin.

(n) Plant Selection. It is important to select the correct type and size of plant required to carry out each task in view of the site conditions, type of material and the outputs required. Plant should be selected so that :

(1) As far as possible, the plant fleet is balanced.

(2) There is sufficient plant to achieve the desired progress of earthwork constructions.

(3) The plant fleet is flexible enough to avoid a major holdup if one item of plant breaks down.

(4) The right type of machine is used for each task.

(5) Each machine is of sufficient capacity to carry out the  earthwork job  effectively and efficiently.

In some instances circumstances may dictate selection of plant other than the ideal. However whatever the plant allocated it is necessary to establish its time of availability, and to estimate the operator hours, plant hours etc… relevant to each task.

(o) Provision of Earthwork. It is essential to determine the order in which work should be carried out and to plan so that operations are not spread out haphazardly as this makes supervision difficult and increases the time lost by plant traveling between tasks. Earthworks job should progress on a face with finishing and trimming being carried out as the work proceeds.

(p) Earthworks Program. The detailed earthwork program should show each major item of work, quantities, timing of operations and plant requirements.

In drawing up the earthworks program the engineer must consider all available alternatives. The earthwork construction program may need to be varied to match the resources available and to even out the demand for particular machines so as to provide continuity of work for them (e.g. a program which requires heavy dossers for six weeks then none for the next two weeks, and finally three for the next twelve weeks, obviously should be re-examined).

As summery of  Pre-construction Planning & Programming of Earthworks ahead of works are begin can be minimize future delays of construction work.