Monday, March 17, 2014

Steps for Construction of Earth roads

today I am going to share with you the steps which are necessary for the construction of the earth roads. 

  • General :
First of all what is an earth road? Earth road is a type of road whose whole pavement section is constructed with the locally available earth material preferably. Borrow pits are located at the nearby sites preferably outside the land width  where, the required earth is available.

Sub-grade and the surface of the earth roads are given larger camber of 1in 33 to 1 in 20 because they need faster drainage to be safe from the moisture. A maximum value of camber of 1 in 20 is the limit because higher camber will result in the formation of cross ruts and corrosion of pavement soils.

  • Specifications of Materials:
The earth material used for the construction of earth roads are termed as satisfactory if they possess the following properties:
                                               Base Course                         Wearing Course

  1. Clay content                       <5%                                      10 to 18%
  2. Silt content                       9 to 32%                                  5 to 15%
  3. Sand content                     60 to 80%                               65 to 80%
  4. Liquid limit                          <35%                                      <35%
  5. Plasticity Index                     <6%                                      4 to 10%
  • Construction steps(Procedure):
Suitable borrow pits are located by doing the survey of the adjacent land which are easy to reach and at economical haulage distance. The various organic materials like trees, shrubs and grass roots are removed before the excavation of the earth.

Location of the centerline: 
The centerline and the road boundaries are marked on the ground by driving the wooden pegs. 

To follow the desired vertical profile of the road, reference pegs are also driven at a certain spacing which depends upon the estimated length of the road construction per day.

Preparation of the subgrade: Following steps are necessary for the preparation of the sub-grade:  (a) Clearing site 
(b) Excavation and construction of fills
(c) Shaping of sub-grade.
The site clearance may be done manually using appliances like spade, pick and hand shovel or using the mechanical equipment like Bulldozer and scraper etc.
Excavation and construction of fills may also be done manually or using the excavation, hauling and compaction equipment.  Dozers are considered very useful for haulage of short distances. 

If the compaction is done manually it will not be sufficient and proper, it should be left to get consolidated under atmospheric conditions. 

Various equipment used by manual labor are shovel, spade, pick-axe, baskets, rammers and hand rollers.                                                        The subgrade should be compacted to the desired grade, camber and longitudinal profile.

Pavement construction: 
The soil is dumped on the prepared sub-grade and pulverized. The soil may be a mixture of more than one soil to get the desired properties. The moisture content is checked and if extra moisture is needed, is added to bring it to OMC.
The soil is mixed, spread and rolled in layers such that the compaction thickness of each layer does not exceed 10 cm. 

The type of roller for compaction is decided based on soil type, desired amount of compaction and availability of equipment. At Least 95% of dry density of I.S. light compaction is considered desirable. The camber of the finished surface is checked and corrected when necessary.

Opening to traffic: The compacted earth surface is allowed to dry out for few days and then is opened to traffic.
Thanks for your kind visit!

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