Unit:3 Road Machineries Note (Highway Engineering -II)

          

 3.1 Methods Of road Construction (Labour based, machine based 

1)  Labour based  (Labour intensive works):-   

 - Takes a lot of time to complete the road project.   

-  Quality of work not be achieved to the required degree.   

-  Small projects, labour intensive work can be adopted.   

-  In Nepal most of contractor preffered.   

-  Work can be done economically.   

2) Machine based (Capital intensive work):-   

-  Take short time period to complete the road project.   

- Construction work can be completed with high degree of quality construction.

-  Useful for big project.   

-  Work can be done costly.   

3.2 Tools, Equipment and Plants Used in Road Construction   

Construction tool, equipment and plants used in road construction activities can be classified as follows.   

A. Tools   

Hand shovel; Chisel; Peak; Spade; Hand rammer; Brushes; Trowel; Wheel borrow etc.

                 

 B. Equipment      

I) Earth Moving Equipment   

-  Dozer (Bull, Angle & Tree)  

   

- Scraper  

  -  Loader   

  -  Excavator   

  

- Dragline

  -Clamshell  

  - Trench digger 

           

II) Compaction Equipment    

-  Smooth wheel roller    

-  Vibrating roller    

-  Pneumatic roller    

-  Sheep foot roller    

-  Different capacity rammers  

III) Leveling Equipment   

- Motor grader    

iv) Paving Equipment    

-  Binder storage tank with heating device    

-  Binder spreader (Distributor)    

-  Aggregate spread    

-  Cement concrete mixture    

-  Bituminous mechanical paver   

-  Cement concrete paver    

v) Lifting Equipment    

-  Backhoe, Loader (for low loads)   

-  Crane (Different capacity)    

Vi)  Transporting Equipment   

-  Dumping trucks (Tippers)    

-  Trucks (Flat body)   

-  Mini dumpers

    vii). Miscellaneous Equipment   

-  Rock driller    

-  Water Tanker/Drilling machines   

C) Plant    

-  Cement concrete plant    

-  Asphalt concrete plant    

-  Cold mix plant    

-  Aggregate crushing plant   

-  Screening plant    

-  Washing plant   

-  Sand blowing unit

   

 3.3 Different types of compacting Equipment

Soil compaction can be achieved in the field either by rolling, ramming or by vibration. Compaction of Sand is also achieved by watering, pounding & jetting.   

 1) Smooth wheel rollers:-   

   There are mainly two types of Smooth wheel rollers :   

a)  Three wheel or macadam rollers with gross weight of 4-18 ton.   

b)  Tandem rollers (two wheel) with gross weight of 1-14 ton.                 

 The compacting efficiency of the smooth wheel rollers depends on the weight, width & diameter of each roller.   

They are useful for finishing operations after compaction of fills & for compacting granular base course of highway. They are suitable for compacting gravel, sand, crushed rock any material where crushing action is required. This is not effective for compaction of deep layer of soil.    

2) Vibrating roller:- 

It is most suited for compacting dry cohesionless granular materials. There are also vibrator is mounted on a roller to give the combined effects of rolling & vibration.  Compact at higher degree compare to the other roller. Vibratory rollers are advantageously used in compacting a wide range of materials.          

 3)  Sheep foot roller/ Sheep roller:-

This type of roller consists of hollow steel cylinder with projecting feet. The efficiency of the sheep foot rollers depends on the weight of the roller & the number of feet in contact with the ground at a time. They are most suitable to compact clayey soils. The weight of the roller can be increased by filling the drum with wet soil.   

 

4)  Pneumatic roller:-

A number of Pneumatic wheels (9-11 Wheels) are mounted on two or more axles under a loading platform. Sandbags or some other weights can be placed over the platform to provide the effective compaction. Light rollers are used for soil layer of small thickness upto 15cm, & heavy rollers useful for layers of thickness upto 20-30cm.   

 The pneumatic tyred rollers are considered to be most suitable to compact nonplastic Silts & fine sands.   

5)  Rammers:-  

 It is useful to compact relatively small areas & where the rollers cannot operate due to space limit. Such as compaction of trenches, foundation & slopes. The output of the rammer is much lower than that of the rollers.