Author: ksenanayake

Categories
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.

Categories
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.

Categories
Road Construction Roadway Excavation

Earth Works – Drilling and Blasting

As the cost of drilling is a significant proportion of the total drilling and blasting operation   the  use  of  as  large  a  drill  hole  as  possible  will  result  in greater hole spacings and reduced footage. However, the choice of hole size and drilling pattern is  frequently  restricted  because  of  the  depth  of  face  possible  and  the  degree  of  fragmentation required.

Material should be produced in a manageable size without the need for additional treatment. In a cut to fill operation, the material size is restricted by the maximum thickness of rock fill that can be compacted by the rollers available. This then places a limit on the drill hole size and spacing. Alternatively,  it  may  be  more  economical  to  hire  larger  rollers  capable  of  compacting  deeper layers.

Deep faces (where possible) offer economy in the use of explosives but, for safety reasons, when using  front  end  loaders  for  loading  of  the  broken  rock,  a  maximum  face  of  10  meters  is recommended.

A  decision  to  drill  and  blast  need  not  slow  down  production.  The  blasting  operation  must  be matched to the capabilities of the earth moving fleet and the total operation should be planned so that intermittent unscheduled blasting does not interfere with the project’s continuity.

Productively  can  be  maintained  by  working  several  faces  and  arranging  blasting  to  be undertaken at times when there is the least likelihood of interruption to other operations.

A blast should be designed to be as large as possible within circumstantial restraints, to ensure that the overall percentage of “Low productivity” material is kept to a minimum and that a minimum of productive time is lost in preparing and moving equipment.

In addition to producing the  necessary quantities, the designed  blast  must achieve a degree of fragmentation which still not adversely effect the cost of handling during succeeding phases of earth moving.  A  well  designed  blast  should  allow  loading  to  be  undertaken  without  any  dozer stockpiling  being  required.  

When blasting adjacent to batters, holes should be more closely spaced and more lightly charged. Unless per-splitting is adopted, all batter holes should be shot on the last delay or shot separately after the main charge had been set off (perimeter blasting). Shooting should always be to a near vertical free face parallel to the holes; and the blast should be designed so that back break and damage to the sub graded and batters is minimized. To avoid such damage, “pin cushion” blasting (no free face) in conjunction with ripping should not be used

Categories
Project Management

PROJECT MANAGEMENT – COST CONTROL

The cost control  of  job  is  the  responsibility  of  the  project manager  but  he expects the construction manager to make sure his day to day expenditure on all items is controlled to Produce the most economical job to the specified standards.

The quantity surveyor is to keep him informed on the current cost situation for the major items.

Factors which add cost to a job and which must be tightly controlled are: –

•    Preliminary site operations (Setting out, haul roads etc)
•    Indirect site expenses (Telephone, electricity, water etc.)
•    Unproductive work items (Fire-breaks, damage to utility lines etc.)
•    Final clean-up.

Fixed  site  expenses,  consisting  mainly  of  costs  of  establishing  and  maintaining  site facilities and the clearing of temporary works and access roads, have all to be controlled tightly.

The initial stages of the job require special control to achieve the desired rate and method of construction. Tight cost control in this phase is essential to see that cost escalation does not set in.

Time  (man  hours  and  machine-hours)  is  the  measure  by  which  all  the  productive  and unproductive effort is controlled against that estimated. It is also used to assess progress against the job program. Time means money. Reduce the time that men and plant spend on an operation and you reduce the cost of the operation.

It is essential that the construction manager/project manager maintains full communication with his quantity surveyor and ensures he is provided promptly with all costing and production information.

Categories
Road Construction Roadway Excavation

Earthmoving Operations-Ripping

The  rippability  of  any  rock  is  materially  affected  by  the  nature  and  composition  of  the  rock. Sedimentary rocks generally offer the best opportunity to rip, whilst metamorphic rocks present
the least opportunity. However decomposed and weathered igneous and metamorphic rocks can often be ripped economically.

Rock with frequent bedding planes and cracks can usually also be ripped economically whereas massive (thickly bedded) rock formations generally must be drilled and blasted.

Some physical characteristics which favor ripping are :-

•    Fractures, faults and planes of weakness of any kind.

•    Weathering resulting from temperature and moisture changes.

•    Brittleness and crystalline nature.

•    Frequent cracks and bedding planes.

•    Large grain size.

•    Moisture permeated clay, shale and rock formations.

•    Low compressive strength.

Ripping will be difficult if the rock formation is :-

•    Massive and homogenous (i.e. lacks bedding planes and cracks).

•    Non crystalline and therefore not brittle.

•    Without planes of weakness.

•    Fine-grained with a solid cementing agent.

•    Of clay origin where moisture may impede ripping because it makes the material plastic.

The following are some further practical matters to be considered when  ripping  –

(1)     When working a cutting always keep the outside deeper than the center. If the center is kept low, all plant tends to work away from the toe of the batter and it is expensive and difficult  to then  excavate the  toe.  In  hard  material,  perimeter  blasting  or  pre-splitting  of batters even when the rest of the cutting is not blasted helps to position the batter toe and tends to stabilize the batter face.

(2)     Rip in straight lines, never turn with the ripper buried as this can result in damage to the tyne tracks and frame.

(3)     Do not leave  blasting until all rippable  material  is removed unless there  is over 3  m of material  still  to  be  excavated.  Shallow  holes  require  an  excessive  footage  of  drilling compared to the volume loosened and as such are uneconomical.

(4)     To obtain penetration the tractor should not be jerked or tracks spun as this causes damage to the unit. Raising the tyne with the hydraulic cylinder will sometimes break out the rock.

(5)     When  working  on  side  drains and  in  the  vicinity  of  batter  toes  the  “radical  arc”  or “adjustable  parallelogram”  rippers  are  preferred  as  the  angle  of  penetration  is  variable, thus enabling material to be both ripped and lifted out.

Categories
Asphalt Paving Road Construction

Asphalt Paving Job Control

For  effective  control  of  asphalt  paving  works  a  comprehensive  understanding  is necessary of each of the following:-

(1)     Specification requirements,
(2)     Plant capabilities,
(3)     Construction processes,
(4)     Inspection requirements.

When faults occur, it is essential that they are quickly recognized, their cause determined and the necessary corrections made promptly.

 Planning of Supervision of Asphalt Paving

Supervision  commences  prior  to  the  start  of  the  asphalt paving,  when  the  engineer  and  project engineer with  contractor’s  manager, laboratory manager  and  supervisor  to  discuss  plans  and  arrangements  for  the carrying out of the works. Matters affecting the quality and timing of the works and the control of traffic that should be discussed, include:-

•    Rate of delivery of asphalt mix to the site,
•    Sequence of operations and safeguards to ensure continuity,
•    Number and types of rollers needed,
•    Matching of asphalt mix supply and paving speed,
•    The chain of command for giving and receiving instructions,
•    Reasons for rejecting the asphalt mix and/or suspending work,
•    Weather and temperature requirements,
•    Traffic control,
•    Lift thickness,
•    Spreading and rolling sequences,
•    Spreading and rolling temperatures,
•    Planning to minimize joints.

Before Paving Starts

Before  the  paving  operation  begins,  a  check  should  be  made  to  see  that  all  necessary inspections and preparations have been carried out. In particular check that:-

(a)     Base or roadway surface is properly prepared,
(b)     Traffic control arrangements are satisfactory,
(c)     Paving and compaction equipment is in good condition and adjustment,
(d)     Hand tools are available on the job,
(e)     Guidelines are in place,
(f)     Asphalt Paver screed is heated to operating temperature,
(g)     Inspectors and supervisors are familiar with the adjustments and settings of the type of
Asphalt Paver  being  used.

Categories
Project Management

Project Management – Materials Control

The effective material control is essential to the efficient management of resources and overall job control. Hence the site engineer must ensure that he: –

• Orders the correct type and quantity of materials.

• Has them in the right place at the desired time. Ordering material well ahead of requirement is essential to the job and assists personnel in Stores and Supply to satisfy the requirements of ALL jobs.

• Checks that the materials are of the specified quality

• Complies  with  all  project specifications(project management) as  to  the  taking  of  natural  materials.  Refer always to material engineer.

Very well material control factors in a project will enhance quality and profit to the project.

Project Management – Plant Control

A similar approach applies to the control of construction plant and equipment and a good supervision ensures that :-

• The  construction company is not being used merely because it is available when other plant, perhaps hired, would be more efficient. The construction manager/project manager, with access to the overall projects in specific area which are closed to perticular project plant needs, should be consulted if an item of plant is not the most suitable for that activity.

• The construction company is such that all items of plant are kept working as efficiently as possible.

• Plant is being skillfully operated and properly maintained.

There  are  occasions  when  the  use  of  a  particular  machine  is  unwise,  as  adverse  site conditions result in a poor job requiring corrective work later. This is undesirable, uneconomical and bad for morale.

Plant requirements are usually included in the works program.

Categories
Project Management

PROJECT CONTROL METHODS

The form of  project control methods  must be simple, easily understood and practical

Factors affecting the degree of project control are:-

• Size of Job.

• Ability of personnel employed on the work.

• The amount of direct supervision that can be given by the site supervisor.

• The rate of construction.

The success of labour control is dependent on regular inspections being carried out and discussions taking place with gangs and crews so that they know what they are expected to do and also the consequences of it not being done.

To supervise effectively, the site supervisor should have a detailed, intimate knowledge of all the construction operations and techniques relating to the work he is to carry out. This requires careful  study  of  the  plans  and  specification  to  understand  what  is  required  and  a  study  of the information  contained  in  the  relevant  project scope  on  how  to  achieve  the necessary results.

For effective project control methods, Other sources of information for the foreman are his site engineer, the construction manager, quantity surveyor, Engineering Laboratary staff, plant managers etc. -remember, when in doubt – ASK.

The  supervisor/foreman/site engineer  must  be  able  to  detect  quickly  any  deficiencies  before  they  become serious. The following rules should be observed :-

• Inspections  must  be  timely,  thorough  and  systematic.  Read the  relevant  clauses  of  the specification just before going out to inspect. Make a list of points which must be checked.  • Make close inspections at the start of operations, e. g. it is better to condemn 10 m3 of faulty material at the start of paving than l00 or 1000 m3 later.

• Observe each operation and think about how it can be simplified or improved.

• Plan  the  testing  and bill of quantites  procedures  of  the  job  to  yield  the  necessary  information promptly and efficiently.

• When deficiencies are observed, decide immediately what corrective action is required and make sure that it is carried out, e. g. when supervising earthmoving operations, do not stand by  and  watch  a  dozer working uphill when it should be working downhill -reconsider and reorganize the plant operations.

• Observe the resources (manpower, materials and plant) that are in use and make an honest assessment of actual need -act accordingly.

Categories
land surveying

Dumpy Level – Land Surveying

  • The simplest type is the Dumpy Level in Land Surveying,the basic components of which are:-
  • A tripod upon which the instrument is attached for use.
  • A tribach, or alternatively a ball and socket, which is used to bring the telescope into a near horizontal position.
  • In dumpy Level, A telescope, fitted with a diaphram on which cross-hairs are etched to define the line of sight.
  • A bubble tube, attached to the telescope tube, and used to determine when the line of sight is horizontal.

 

Tripod

The tripod consists of three pointed legs, (wooden or metal), with a solid metal head. The legs may be rigid or telescopic.

For good leveling it is essential that there be no movement or free-play in any of the joints. The metal feet on the legs, the sliding joints of telescopic legs and the hinged attachments
to the head should be checked and adjusted regularly.

Wooden legs should be painted at least once each six months with a 50/50 mixture of linseed oil and turpentine.

 Tribach

The tribach consists of two plates (one upper – the other lower) joined by three adjustable foot- screws.

The tribach is permanently fixed to the telescope and its axis, in such a way that the upper plate is parallel to the telescope tube.

The three foot screws are manipulated to bring the upper plate and the telescope into a horizontal position.

The tribach may be screwed onto the head of the tripod, or alternatively a central screw within the tripod head may be screwed into the base of the tribach.

For “quickset” levels the three screw tribach is replaced by a ball and socket unit which performs the same function.

The upper plates of tribachs or ball and socket units may be fitted with a small pea, or centre bubble, so that quick approximate setting up of the instrument can be carried out.

The tribach should fit firmly to the tripod head with no free-play and there should be no sloppiness in the movement of foot-screws. A protector for the tripod head screws is provided and should always be used. Foot screws should be kept free of dust and lightly oiled with fine oil as required.

Categories
Project Management

THE AIM OF CONTRACT INSPECTION

When a contract for road works is let, the contractor undertakes to carry out the work to the job plans and specifications, at a given price, in a specific time.
The aim of contract inspection is to ensure that the Employer’s requirements, as detailed in the contract documents, and as agreed between the principal and the contractor , are fulfilled by the due date for completion .
There are three important elements in the above statement.
·  The Employer’s requirements are specified and agreed.
·  The inspector must ensure that these requirements are fulfilled.
·  There is a time specified

DEFINITIONS

Before proceeding, it is important to define the terms to be used. The following definitions are in accordance with the meaning assigned to the terms in the Road Development Authority’s General Conditions of Contract

·  A Contract is an agreement between two parties – the “Employer” and “the contractor” – that for some consideration and under certain conditions, the contractor will do certain work as specified and agreed , for the Employer.

·  The Employer usually the Road Development Authority of Main Roads is the party to the contract who stipulates the work and the standard of workmanship required , and who in the first instance nominates the conditions under which a contract will be entered into.

·  The contractor is the person or company who offers to execute the works for the Employer for a certain consideration and whose offer is accepted by the Employer.

·  The Engineer is the person nominated in the contract, usually the Consultant Engineer, whom both parties agree should impartially ensure that both the Employer and the contractor properly perform their respective obligations under the contract

The engineer’s Representative is the person to whom the engineer has delegated all or some of his powers under the contract. On Highway/Expressway contracts he is normally called the Team Leader(Foreign Funded JBIC)/Resident Engineer(ADB). The Assistant Resident Engineer or Chief Engineer/project Engineer is responsible for the detailed supervision and administration necessary to achieve the completion of the project within the terms of the contract.

He must also make certain , by way of site inspection and control, that the design adopted is adequate to meet the physical and geological conditions encountered on site once work has commenced.

It is important that the all the  definitions are read carefully in contract, even though they may seem complex. Understanding of definitions is most important to a proper understanding of the principles of contract inspection.